Rock and Minerals

Andesite

-- a dark, fine-grained, brown or grayish volcanic rock that is intermediate in composition between rhyolite and basalt. texture= Andesite is the name used for a family of fine-grained, extrusive igneous rocks that are usually light to dark gray in color. They often weather to various shades of brown, and these specimens must be broken for proper examination. Andesite is rich in plagioclase feldspar minerals and may contain biotite, pyroxene, or amphibole. Andesite usually does not contain quartz or olivine. Andesite is typically found in lava flows produced by stratovolcanoes. Because these lavas cooled rapidly at the surface, they are generally composed of small crystals. The mineral grains are usually so small that they cannot be seen without the use of a magnifying device. Some specimens that cooled rapidly contain a significant amount of glass, while others that formed from gas-charged lavas have a vesicular or amygdaloidal texture. For a fine-grained rock like andesite, these classifications are impossible to use precisely when in the field or the classroom. They require chemical or mineralogical analyses that are usually not available, affordable, or practical. If you examine a rock that appears to be andesite, but you are not confident that it meets the mineralogical or chemical classification of andesite, you can properly call it an "andesitic" rock. That means that while the rock looks like andesite, a microscopic examination or chemical testing might prove you wrong! Environments of formation=Andesite and diorite are common rocks of the continental crust above subduction zones. They generally form after an oceanic plate melts during its descent into the subduction zone to produce a source of magma. Diorite is a coarse-grained igneous rock that forms when the magma did not erupt, but instead slowly crystallized within Earth's crust. Andesite is a fine-grained rock that formed when the magma erupted onto the surface and crystallized quickly. Andesite and diorite have a composition that is intermediate between basalt and granite. This is because their parent magmas formed from the partial melting of a basaltic oceanic plate. This magma may have received a granitic contribution by melting granitic rocks as it ascended or mixed with granitic magma. Andesite derives its name from the Andes Mountains of South America. In the Andes it occurs as lava flows interbedded with ash and tuff deposits on the steep flanks of stratovolcanoes. Andesite stratovolcanoes are found above subduction zones in Central America, Mexico, Washington, Oregon, the Aleutian Arc, Japan, Indonesia, the Philippines, the Caribbean, and New Zealand, among other locations. Andesite can also form away from the subduction zone environment. For example, it can form at ocean ridges and oceanic hotspots from partial melting of basaltic rocks. It can also form during eruptions at continental plate interiors where deep-source magma melts continental crust or mixes with continental magmas. There are many other environments where andesite might form. Water vapor produced when ocean-floor sediments on an oceanic plate are heated in a subduction zone. Water vapor produced when hydrous minerals dehydrate in the heat of a subduction zone.Carbon dioxide produced when rising magma encounters carbonate rocks, such as limestone, marble, or dolomite. Water vapor produced when a rising magma chamber encounters groundwater. At depth, these gases can be dissolved in the magma like carbon dioxide dissolved in a can of cold beer. If that can of beer is shaken and suddenly depressurized by opening the can, the gas and the beer will erupt from the opening. A volcano behaves in a similar manner. A rising magma chamber instantly depressurized by a landslide, faulting, or other event can produce a similar but much larger explosive eruption. composition= Andesite most commonly denotes fine-grained, usually porphyritic rocks; in composition these correspond roughly to the intrusive igneous rock diorite and consist essentially of andesine (a plagioclase feldspar) and one or more ferromagnesian minerals, such as pyroxene or biotite. Smaller amounts of sanidine, a potassium-rich feldspar, may be present. The larger crystals of feldspar and ferromagnesian minerals are often visible to the naked eye; they lie in a finer groundmass, usually crystalline, but sometimes glassy. There are three subdivisions of this rock family: the quartz-bearing andesites, or dacites, sometimes considered to be a separate family; the hornblende- and biotite-andesites; and the pyroxene-andesites. The dacites contain primary quartz, which may appear in small blebs or crystals or only as minute interstitial grains in the groundmass. The hornblende- and biotite-andesites are comparatively rich in feldspar and are usually pale pink, yellow, or gray. Pyroxene-andesites are the commonest type of andesite and occur in amounts comparable to basalt. They are darker, denser, more basic rocks. The composition of andesite is classified as "intermediate" among igneous rocks, implying that its silica content is in the range of 52-63 percent. Its texture ranges from aphanitic to porphyritic.[1] The mineral assembly is typically dominated by plagioclase, with pyroxene and/or hornblende. Biotite, quartz, magnetite, and sphene are common accessory minerals. Alkali feldspar may be present in minor amounts.

Coquina

--a soft limestone of broken shells, used in road-making in the Caribbean and Florida. Environments of formation= Coquina Rock was formed during the Pleistocene Ice Age, approximately from 1.8 million years ago, until approximately 11,550 years ago. The end of the Pleistocene Era corresponds with the retreat of the last continental glacier. Florida itself, and its landmass, was rising from the sea, and Coquina rock began forming along a long portion of Florida's East Coast, in the latter part of this era, and the global warming period that came with it. Marine life before the Ice age flourished in the seas, and again after the receding ice, marine abundance quickly recovered. Coquina Rock, and Florida became, as we know it today. Coquina rock, geologically known as Donak Variabilis, is mainly composed of incompletely consolidated sedimentary rock. It is formed of billions of small clam-like seashell, called Coquina, or cockleshell. Overall composition of most Coquina rock is a mixture of these small marine clams, crushed oyster shell, mollusk shell, fragmented fossils, fragmented coral, crinoids, limestone, red sand, white sand, phosphate, calcite, and perhaps a little clay. It is relatively soft when quarried, and hardens over the years, after surface exposure. Coquina rock, as it exists today, was formed along the East Coast of Florida. Formations can be found near the coast, from Palm Beach, Florida, then Northward to South of Jacksonville, Florida. Coquina rock can be found as far as 20 miles inland, and most deposits follow the Eastern Coast, and along the now I-95 corridor. Florida is not the only place it is found, as variations can extend into North Carolina. Coquina, and very similar formations of it, can also be found in many places around the world. The Coquina rock sold at CoquinaRock.com comes from the Northern end of Volusia County, and the Southern end of Flagler County. It is known as The Bulow Strain Series, or The Bulow Strain of Coquina rock. Many people believe the rock from here is the prettiest, because of the Orange color tint variations, and the extensive ocean wear, and sculptured look of the ones found here. So much so, that rocks from here are preferred, and can be found in uses all over Florida. The orange tint comes from the heavier mixture of this area's red sand. Coquina from other areas will vary in color, most of them lighter in color, due to their dominant mixture of lighter sand, and whiter sea shell, oyster shell, and limestone. Consistency and texture from our Bulow Strain Coquina can also vary, as the seas washed and moved different concentrations of each aggregate, in different quantity, and different depth, when forming. You may have noticed that many Coquina rocks have "holes" or "half-moon" indentations in them, and ask how the hole got there, or if it was drilled into the rock. The answer is simple, that is where a palm tree, or even a large hardwood tree, grew at one time, as the rock was forming. When the tree and root base expired and decayed away, the hole remains. //Coquina forms near shore, where wave action is vigorous and sorts the sediments well. Most limestones have some fossils in them, and many have beds of shell hash, but coquina is the extreme version. A well-cemented, strong version of coquina is called coquinite. A similar rock, composed chiefly of shelly fossils that lived where they sit, unbroken and unabraded, is called a coquinoid limestone. composition= calcite *texture= clastic*

Sandstone

--sedimentary rock consisting of sand or quartz grains cemented together, typically red, yellow, or brown in color. Sandstone is a sedimentary rock composed of sand-size grains of mineral, rock, or organic material. It also contains a cementing material that binds the sand grains together and may contain a matrix of silt- or clay-size particles that occupy the spaces between the sand grains. Sandstone is one of the most common types of sedimentary rock and is found in sedimentary basins throughout the world. It is often mined for use as a construction material or as a raw material used in manufacturing. In the subsurface, sandstone often serves as an aquifer for groundwater or as a reservoir for oil and natural gas. Environments of formation= The grains of sand in a sandstone are usually particles of mineral, rock, or organic material that have been reduced to "sand" size by weathering and transported to their depositional site by the action of moving water, wind, or ice. Their time and distance of transport may be brief or significant, and during that journey the grains are acted upon by chemical and physical weathering. If the sand is deposited close to its source rock, it will resemble the source rock in composition. However, the more time and distance that separate the source rock from the sand deposit, the greater its composition will change during transport. Grains that are composed of easily-weathered materials will be modified, and grains that are physically weak will be reduced in size or destroyed. If a granite outcrop is the source of the sand, the original material might be composed of grains of hornblende, biotite, orthoclase, and quartz. Hornblende and biotite are the most chemically and physically susceptible to destruction, and they would be eliminated in the early stage of transport. Orthoclase and quartz would persist longer, but the grains of quartz would have the greatest chance of survival. They are more chemically inert, harder, and not prone to cleavage. Quartz is typically the most abundant type of sand grain present in sandstone. It is extremely abundant in source materials and is extremely durable during transport. The grains in a sandstone can be composed of mineral, rock, or organic materials. Which and in what percentage depends upon their source and how they have suffered during transport. Mineral grains in sandstones are usually quartz. Sometimes the quartz content of these sands can be very high - up to 90% or more. These are sands that have been worked and reworked by wind or water and are said to be "mature." Other sands can contain significant amounts of feldspar, and if they came from a source rock with a significant quartz content they are said to be "immature." texture= Texture and mineralogical properties are used for sandstone classification, though considerable debate exists as to which properties to emphasize. The two major classes of sandstone are arenite and wacke. The boundary between the two is based on the amount of matrix present in the sample. Arenites contain less matrix than wacke. Though the exact boundary is debated, often 5 percent matrix is the accepted value, whereas some experts place this boundary at 15 percent. Another common classification uses the name arkose for rocks rich in feldspar. These names are further modified by the components present in the rock. Lithic arenite, feldspathic wacke, and quartz arenite are common examples. composition= Sandstone (sometimes known as arenite) is a clastic sedimentary rock composed mainly of sand-sized minerals or rock grains. Most sandstone is composed of quartz or feldspar because these are the most common minerals in the Earth's crust. texture - clastic (only noticeable with a microscope). Grain size - 0.06 - 2mm; clasts visible to the naked eye, often identifiable. Hardness - variable, soft to hard, dependent on clast and cement composition. Colour - variable through grey, yellow, red to white reflecting the variation in mineral content and cement. Clasts - dominantly quartz and feldspar (orthoclase, plagioclase) with lithic clasts and varying minor amounts of other minerals. Other features - gritty to touch (like sandpaper). Uses - if soft then generally of no use; if hard then can be used as aggregate, fill etc. in the construction and roading industries; dimension stone for buildings, paving, etc

Shale

--soft, finely stratified sedimentary rock that formed from consolidated mud or clay and can be split easily into fragile slabs. Shale is a fine-grained sedimentary rock that forms from the compaction of silt and clay-size mineral particles that we commonly call "mud." This composition places shale in a category of sedimentary rocks known as "mudstones." Shale is distinguished from other mudstones because it is fissile and laminated. "Laminated" means that the rock is made up of many thin layers. "Fissile" means that the rock readily splits into thin pieces along the laminations. composition= Shale is a rock composed mainly of clay-size mineral grains. These tiny grains are usually clay minerals such as illite, kaolinite, and smectite. Shale usually contains other clay-size mineral particles such as quartz, chert, and feldspar. Other constituents might include organic particles, carbonate minerals, iron oxide minerals, sulfide minerals, and heavy mineral grains. These "other constituents" in the rock are often determined by the shale's environment of deposition, and they often determine the color of the rock. texture= Shale is a fine-grained, clastic sedimentary rock composed of mud that is a mix of flakes of clay minerals and tiny fragments (silt-sized particles) of other minerals, especially quartz and calcite. The ratio of clay to other minerals is variable. Environments of formation= Shale starts with bits of rock that erode off of larger rocks from contact with moving water and the weather. Very fine particles of feldspar, quartz, mica, pyrite and other minerals settle to the bottom of still bodies of water, such as swamplands, deep parts of the ocean and deep, still lakes. The fine rock particles mix with decaying organic matter into a mud. Because weathering is a continual process, new layers are always building up. The top layers press on the bottom layers with more and more pressure. When enough pressure builds up, the bottom layers become rock through a process called lithification. Lithification causes the thin layers that are characteristic of shale. Shale is a soft rock that breaks easily. The color varies depending on the exact minerals that formed the shale. Red, green and black are some color variations. Geologists classify shale as a claystone due to the small size of the particles that form the rock. Shale is a common rock that makes up much of Earth's crust. Shale, like all sedimentary rocks, forms as a result of the compaction and cementation of materials that have weathered and eroded off of other, pre-existing rocks. These pre-existing rocks can be igneous, metamorphic or even other sedimentary rocks. For shale, it specifically forms from a muddy mixture of clay minerals (like kaolinite, montmorillonite or illite) and silicates (like quartz or chert). Some deposits also contain traces of mica minerals, which tend to give the rocks a greenish color, or iron minerals, which will give the rocks a reddish color. Browns and yellow browns are also possible but not as common. Most of the oil and natural gas-bearing shales tend to be dark gray to black in color, due to the large amounts of organic matter they contain. Eventually the minerals in the mud settle out of the liquid mud solution and become compacted. It is this compacting that allows for rock formation, rather than remaining a permanent mud deposit. This settling out and compaction process can only happen in slow moving to still water bodies, such as lakes or deltas, where there is little water flow to prevent the settling out process from occurring. You can also sometimes see shale deposits along continental shelves, where again, the water currents would be slow moving. //Shales are often found with layers of sandstone or limestone. They typically form in environments where muds, silts, and other sediments were deposited by gentle transporting currents and became compacted, as, for example, the deep-ocean floor, basins of shallow seas, river floodplains, and playas. Most shales occur in extensive sheets several metres thick, though some develop in lenticular formations. Shales characteristically consist of at least 30 percent clay minerals and substantial amounts of quartz. They also contain smaller quantities of carbonates, feldspars, iron oxides, fossils, and organic matter. Some organic-rich shales, called oil shales, contain kerogen (a chemically complex mixture of solid hydrocarbons derived from plant and animal matter) in large enough quantities to yield oil when subjected to intense heat. Shales typically have a laminated structure and are fissile; i.e., they exhibit a tendency to split into thin layers that are usually parallel to the bedding-plane surface. Such physical properties as permeability and plasticity are largely dependent on the grain sizes of the constituent minerals. Shales' colour is determined primarily by composition. In general, the higher the organic content of a shale, the darker its colour. The presence of hematite and limonite (hydrated ferric oxide) gives rise to reddish and purple colouring, while mineral components rich in ferrous iron impart blue, green, and black hues. Calcareous shales (those having a large percentage of calcite), on the other hand, are light gray or yellowish.

Bituminous

--black coal having a relatively high volatile content. It burns with a characteristically bright smoky flame. --of, containing, or of the nature of bitumen. Environments of formation= Coal forms from the accumulation of plant debris, usually in a swamp environment. When a plant dies and falls into the swamp, the standing water of the swamp protects it from decay. Swamp waters are usually deficient in oxygen, which would react with the plant debris and cause it to decay. This lack of oxygen allows the plant debris to persist. In addition, insects and other organisms that might consume the plant debris on land do not survive well under water in an oxygen-deficient environment. To form the thick layer of plant debris required to produce a coal seam, the rate of plant debris accumulation must be greater than the rate of decay. Once a thick layer of plant debris is formed, it must be buried by sediments such as mud or sand. These are typically washed into the swamp by a flooding river. The weight of these materials compacts the plant debris and aids in its transformation into coal. About ten feet of plant debris will compact into just one foot of coal. Plant debris accumulates very slowly. So, accumulating ten feet of plant debris will take a long time. The fifty feet of plant debris needed to make a five-foot thick coal seam would require thousands of years to accumulate. During that long time, the water level of the swamp must remain stable. If the water becomes too deep, the plants of the swamp will drown, and if the water cover is not maintained the plant debris will decay. To form a coal seam, the ideal conditions of perfect water depth must be maintained for a very long time.If you are an astute reader you are probably wondering: "How can fifty feet of plant debris accumulate in water that is only a few feet deep?" The answer to that question is the primary reason that the formation of a coal seam is a highly unusual occurrence. It can only occur under one of two conditions: 1) a rising water level that perfectly keeps pace with the rate of plant debris accumulation; or, 2) a subsiding landscape that perfectly keeps pace with the rate of plant debris accumulation. Most coal seams are thought to have formed under condition #2 in a delta environment. On a delta, large amounts of river sediments are being deposited on a small area of Earth's crust, and the weight of those sediments causes the subsidence. For a coal seam to form, perfect conditions of plant debris accumulation and perfect conditions of subsidence must occur on a landscape that maintains this perfect balance for a very long time. It is easy to understand why the conditions for forming coal have occurred only a small number of times throughout Earth's history. The formation of a coal requires the coincidence of highly improbable events. //Bituminous coal or black coal is a relatively soft coalcontaining a tarlike substance called bitumen. It is of higher quality than lignite coal but of poorer quality than anthracite. Formation is usually the result of high pressure being exerted on lignite. texture= grain size/texture- fine; description/formation- smooth surface and hardened mud ... composition= The composition of bituminous coal can and does vary from one deposit to the next. However, all bituminous coal is 45 to 86% carbon. Adhesion: Bitumen has the ability to adhere to a solid surface in a fluid state depending on the nature of the surface. The presence of water on the surface will prevent adhesion. Resistance to Water: Bitumen is water resistant. Under some conditions water may be absorbed by minute quantities of inorganic salts in the bitumen or filler in it. Hardness: To measure the hardness of bitumen, the penetration test is conducted, which measures the depth of penetration in tenths of mm. of a weighted needle in bitumen after a given time, at a known temperature. Commonly a weight of 100 gm is applied for 5 sec at a temperature of 77 °F. The penetration is a measure of hardness. Typical results are 10 for hard coating asphalt, 15 to 40 for roofing asphalt and up to 100 or more for waterproofing bitumen. Viscosity and Flow: The viscous or flow properties of bitumen are of importance both at high temperature during processing and application and at low temperature to which bitumen is subjected during service. The flow properties of bitumens vary considerably with temperature and stress conditions. Deterioration, or loss of the desirable properties of bitumen, takes the form of hardening. Resultantly, decrease in adhesive and flow properties and an increase in the softening point temperature and coefficient of thermal expansion. Softening point: Softening point is the temperature at which a steel ball falls a known distance through the bitumen when the test assembly is heated at a known rate. Usually the test consist of a (3/8)in dia steel ball, weight 3.5 gm, which is allowed to sink through a (5/8) in dia, (1/4) in thick disk of bitumen in a brass ring. The whole assembly is heated at a rate of 9 °F per min. Typical values would be 240 °F for coating grade asphalts, 140 °F to 220 °F for roofing asphalt and down to 115 °F for bituminous waterproofing material. Ductility: Ductility test is conducted to determine the amount bitumen will stretch at temperature below its softening point. A briquette having a cross sectional area of 1 in2 is placed in a tester at 77 °F. Ductility values ranges from 0 to over 150 depending on the type of bitumen.

Schist [garnet]

Schist is medium grade metamorphic rock, formed by the metamorphosis of mudstone / shale, or some types of igneous rock, to a higher degree than slate, i.e. it has been subjected to higher temperatures and pressures. The resulting foliation is coarser and more distinct than that of slate due to the higher degree of crystallisation of mica minerals (biotite, chlorite, muscovite) forming larger crystals, and is often referred to as schistosity. These larger crystals reflect light so that schist often has a high lustre, i.e. it is shiny. Porphyroblasts are common in schist, and they provide information on the temperature and pressure conditions under which the rock formed. Due to the more extreme formation conditions, schist often shows complex folding patterns. There are many varieties of schist and they are named for the dominant mineral comprising the rock, e.g. mica schist, green schist (green because of high chlorite content), garnet schist etc. Texture - foliated, foliation on mm to cm scale. Grain size - fine to medium grained; can often see crystals with the naked eye. Hardness - generally hard. Colour - variable - often alternating lighter and darker bands, often shiny. Mineralogy - mica minerals (biotite, chlorite, muscovite), quartz and plagioclase often present as monomineralic bands, garnet porphyroblasts common. Other features - generally smoothish to touch. Uses - generally used as a decorative rock, e.g. walls, gardens etc; high percentage of mica group minerals precludes its use in the construction and roading industries. New Zealand occurrences - extensive occurrence throughout the South Island, e.g. Southern Alps, Central Otago area. composition=Garnet is the name used for a large group of rock-forming minerals. These minerals share a common crystal structure and a generalized chemical composition of X3Y2(SiO4)3. In that composition, "X" can be Ca, Mg, Fe2+ or Mn2+, and "Y" can be Al, Fe3+, Mn3+, V3+ or Cr3+. These minerals are found throughout the world in metamorphic, igneous, and sedimentary rocks. Most garnet found near Earth's surface forms when a sedimentary rock with a high aluminum content, such as shale, is subjected to heat and pressure intense enough to produce schist or gneiss. Garnet is also found in the rocks of contact metamorphism, subsurface magma chambers, lava flows, deep-source volcanic eruptions, and the soils and sediments formed when garnet-bearing rocks are weathered and eroded. Most people associate the word "garnet" with a red gemstone; however, they are often surprised to learn that garnet occurs in many other colors and has many other uses. In the United States, the major industrial uses of garnet in 2012 were waterjet cutting (35%), abrasive blasting media (30%), water filtration granules (20%), and abrasive powders (10%). Environments of formation= Most garnet forms at convergent plate boundarieswhere shale is being acted upon by regional metamorphism. The heat and pressure of metamorphism breaks chemical bonds and causes minerals to recrystallize into structures that are stable under the new temperature-pressure environment. The aluminum garnet, almandine, generally forms in this environment. As these rocks are metamorphosed, the garnets start as tiny grains and enlarge slowly over time as metamorphism progresses. As they grow, they displace, replace, and include the surrounding rock materials. The photo below shows a microscopic view of a garnet grain that has grown within a schist matrix. It included a number of the host rock's mineral grains as it grew. This explains why so many garnets formed by regional metamorphism are highly included.

Alabaster

Variety of Gypsum Composition: dihydrate calcium sulphate Color: White, pink, brownish Streak: White Crystal system: Monoclinic Crystal forms: The crystal form is hexagonal and often glassy in appearance. Transparency: Transparent to Opaque Fracture: Splintery Tenacity: Flexible, inelastic Luster: Vitreous Cleavage: 1,1

Kaolinite

composition= basic aluminum silicate color= White, gray, yellow, beige. May also be darker colored brown, orange, or reddish-brown from iron oxide impurities. streak= white Crystal system= monoclinic Crystal form= Most often as unshaped compact masses. Crystals are micro crystalline as tiny grains and plates. Crystals are rarely visible to the naked eye. transparency= Opaque. Rarely translucent. luster= dull fracture= earthy cleavage= 1,1

Antracite

--coal of a hard variety that contains relatively pure carbon and burns with little flame and smoke. Anthracites are black to steel gray in colour and have a brilliant, almost metallic lustre. They can be polished and used for decorative purposes. Hard and brittle, anthracites break with conchoidal fracture into sharp fragments. Unlike many bituminous coals, they are clean to the touch. Although anthracites are difficult to ignite, they burn with a pale blue flame and require little attention to sustain combustion. In the past they were used for domestic heating because they produce little dust upon handling, burn slowly, and emit relatively little smoke. Anthracite is rarely used for this purpose today because of its limited abundance and relatively high cost and the ready availability of other sources of energy (e.g., natural gas and electricity) for heating purposes. Although anthracites usually occur in geologically deformed areas, such as in the intensely folded sedimentary rocks of the anthracite region of Pennsylvania, U.S., their origin is due to higher than normal heating caused by the presence of nearby igneous intrusions or high geothermal gradients. Both of these phenomena produce temperatures much higher than those reached at depth in most sedimentary basins. For instance, in Antarctica, large igneous sills intruded the coal measures and converted some of the existing bituminous coal to anthracite. Temperatures ranging from 170 to 250 °C (about 340 to 480 °F) are thought to be necessary for the formation of anthracite. Coal is an organic sedimentary rock that forms from the accumulation and preservation of plant materials, usually in a swamp environment. Coal is a combustible rock and, along with oil and natural gas, it is one of the three most important fossil fuels. Coal has a wide range of uses; the most important use is for the generation of electricity. Environments of formation= Coal forms from the accumulation of plant debris, usually in a swamp environment. When a plant dies and falls into the swamp, the standing water of the swamp protects it from decay. Swamp waters are usually deficient in oxygen, which would react with the plant debris and cause it to decay. This lack of oxygen allows the plant debris to persist. In addition, insects and other organisms that might consume the plant debris on land do not survive well under water in an oxygen-deficient environment. To form the thick layer of plant debris required to produce a coal seam, the rate of plant debris accumulation must be greater than the rate of decay. Once a thick layer of plant debris is formed, it must be buried by sediments such as mud or sand. These are typically washed into the swamp by a flooding river. The weight of these materials compacts the plant debris and aids in its transformation into coal. About ten feet of plant debris will compact into just one foot of coal. Plant debris accumulates very slowly. So, accumulating ten feet of plant debris will take a long time. The fifty feet of plant debris needed to make a five-foot thick coal seam would require thousands of years to accumulate. During that long time, the water level of the swamp must remain stable. If the water becomes too deep, the plants of the swamp will drown, and if the water cover is not maintained the plant debris will decay. To form a coal seam, the ideal conditions of perfect water depth must be maintained for a very long time. If you are an astute reader you are probably wondering: "How can fifty feet of plant debris accumulate in water that is only a few feet deep?" The answer to that question is the primary reason that the formation of a coal seam is a highly unusual occurrence. It can only occur under one of two conditions: 1) a rising water level that perfectly keeps pace with the rate of plant debris accumulation; or, 2) a subsiding landscape that perfectly keeps pace with the rate of plant debris accumulation. Most coal seams are thought to have formed under condition #2 in a delta environment. On a delta, large amounts of river sediments are being deposited on a small area of Earth's crust, and the weight of those sediments causes the subsidence. For a coal seam to form, perfect conditions of plant debris accumulation and perfect conditions of subsidence must occur on a landscape that maintains this perfect balance for a very long time. It is easy to understand why the conditions for forming coal have occurred only a small number of times throughout Earth's history. The formation of a coal requires the coincidence of highly improbable events. composition= Further identification of non-foliated rocks is dependent on the composition of the minerals or components in the rock. Anthracite coal is similar to bituminous coal. Both are black in color , and is composed of carbon. texture= Amorphous, Glassy. The texture of anthracite coal (black coal) is rough in that it is a rock, but it has a smooth, almost slippery quality as well.

Marble

Environments of formation=Most marble forms at convergent plate boundaries where large areas of Earth's crust are exposed to regional metamorphism. Some marble also forms by contact metamorphism when a hot magma body heats adjacent limestone or dolostone. Before metamorphism, the calcite in the limestone is often in the form of lithified fossil material and biological debris. During metamorphism, this calcite recrystallizes and the texture of the rock changes. In the early stages of the limestone-to-marble transformation, the calcite crystals in the rock are very small. In a freshly-broken hand specimen, they might only be recognized as a sugary sparkle of light reflecting from their tiny cleavage faces when the rock is played in the light. As metamorphism progresses, the crystals grow larger and become easily recognizable as interlocking crystals of calcite. Recrystallization obscures the original fossils and sedimentary structures of the limestone. It also occurs without forming foliation, which normally is found in rocks that are altered by the directed pressure of a convergent plate boundary. Recrystallization is what marks the separation between limestone and marble. Marble that has been exposed to low levels of metamorphism will have very small calcite crystals. The crystals become larger as the level of metamorphism progresses. Clay minerals within the marble will alter to micas and more complex silicate structures as the level of metamorphism increases. Color: Marble is usually a light-colored rock. When it is formed from a limestone with very few impurities, it will be white in color. Marble that contains impurities such as clay minerals, iron oxides, or bituminous material can be bluish, gray, pink, yellow, or black in color. Marble of extremely high purity with a bright white color is very useful. It is often mined, crushed to a powder, and then processed to remove as many impurities as possible. The resulting product is called "whiting." This powder is used as a coloring agent and filler in paint, whitewash, putty, plastic, grout, cosmetics, paper, and other manufactured products. Acid Reaction: Being composed of calcium carbonate, marble will react in contact with many acids, neutralizing the acid. It is one of the most effective acid neutralization materials. Marble is often crushed and used for acid neutralization in streams, lakes, and soils. It is used for acid neutralization in the chemical industry as well. Pharmaceutical antacid medicines such as "Tums" contain calcium carbonate, which is sometimes made from powdered marble. These medicines are helpful to people who suffer from acid reflux or acid indigestion. Powdered marble is used as an inert filler in other pills. Hardness: Being composed of calcite, marble has a hardness of three on the Mohs hardness scale. As a result, marble is easy to carve, and that makes it useful for producing sculptures and ornamental objects. The translucence of marble makes it especially attractive for many types of sculptures. The low hardness and solubility of marble allows it to be used as a calcium additive in animal feeds. Calcium additives are especially important for dairy cows and egg-producing chickens. It is also used as a low-hardness abrasive for scrubbing bathroom and kitchen fixtures. Ability to Accept a Polish: After being sanded with progressively finer abrasives, marble can be polished to a high luster. This allows attractive pieces of marble to be cut, polished, and used as floor tiles, architectural panels, facing stone, window sills, stair treads, columns, and many other pieces of decorative stone. Grade of metamorphism= t is a rock of intermediate metamorphic grade between phyllite and gneiss. The specimen shown above is a "chlorite schist" because it contains a significant amount of chlorite. It is about two inches (five centimeters) across. Texture - granular. Grain size - medium grained; can see interlocking calcite crystals with the naked eye. Hardness - hard, although component mineral is soft (calcite is 3 on Moh's scale of hardness). Colour - variable - pure marble is white but marble exists in a wide variety of colours all the way through to black . Mineralogy - calcite. Other features - generally gritty to touch. Uses - building stone; dimension stone for building facings, paving etc; cut into blocks and cut for monuments, headstones etc (wears over time due to softness of calcite, prone to acid rain damage [calcite is soluble in acid]); whiting material in toothpaste, paint and paper. New Zealand occurrences - Northland (Marble Bay), northwest Nelson (Arthur Marble), Canterbury, Fiordland, Stewart Island. composition= marble is a metamorphic rock that may be foliated or non-foliated, composed of recrystallized carbonate minerals, most commonly calcite or dolomite. Geologists use the term "marble" to refer to metamorphosed limestone; however, stonemasons use the term more broadly to encompass unmetamorphosed limestone.

Basalt

texture= Basalt is a dark-colored, fine-grained, igneous rock composed mainly of plagioclase and pyroxene minerals. It most commonly forms as an extrusive rock, such as a lava flow, but can also form in small intrusive bodies, such as an igneous dike or a thin sill. It has a composition similar to gabbro. The difference between basalt and gabbro is that basalt is a fine-grained rock while gabbro is a coarse-grained rock. Environments of formation= Most of the basalt found on Earth was produced in just three rock-forming environments: 1) oceanic divergent boundaries, 2) oceanic hotspots, and 3) mantle plumes and hotspots beneath continents. The images on this page feature some of these basalt-forming environments. Most of Earth's basalt is produced at divergent plate boundaries on the mid-ocean ridge system (see map). Here convection currents deliver hot rock from deep in the mantle. This hot rock melts as the divergent boundary pulls apart, and the molten rock erupts onto the sea floor. These submarine fissure eruptions often produce pillow basalts as shown in the image on this page. The active mid-ocean ridges host repeated fissure eruptions. Most of this activity is unnoticed because these boundaries are under great depths of water. At these deep locations, any steam, ash, or gas produced is absorbed by the water column and does not reach the surface. Earthquake activity is the only signal to humans that many of these deep ocean ridge eruptions provide. However, Iceland is a location where a mid-ocean ridge has been lifted above sea level. There, people can directly observe this volcanic activity. Another location where significant amounts of basalt are produced is above oceanic hotspots. These are locations (see map above) where a small plume of hot rock rises up through the mantle from a hotspot on Earth's core. The Hawaiian Islands are an example of where basaltic volcanoes have been built above an oceanic hotspot. Basalt production at these locations begins with an eruption on the ocean floor. If the hotspot is sustained, repeated eruptions can build the volcanic cone larger and larger until it becomes high enough to become an island. All of the islands in the Hawaiian Island chain were built up from basalt eruptions on the sea floor. //Basalt is used for a wide variety of purposes. It is most commonly crushed for use as an aggregate in construction projects. Crushed basalt is used for road base, concrete aggregate, asphalt pavement aggregate, railroad ballast, filter stone in drain fields, and may other purposes. Basalt is also cut into dimension stone. Thin slabs of basalt are cut and sometimes polished for use as floor tiles, building veneer, monuments, and other stone objects. --Basalt is a common extrusive igneous rock formed from the rapid cooling of basaltic lava exposed at or very near the surface of a planet or moon. Flood basalt describes the formation in a series of lava basalt flows. Group - volcanic. Colour - dark grey to black. Texture - aphanitic (can be porphyritic). Mineral content - groundmass generally of pyroxene (augite), plagioclase and olivine, possibly with minor glass; if porphyritic the phenocrysts will be any of olivine, pyroxene or plagioclase. Silica (SiO2) content - 45%-52%. Uses - aggregate, fill etc. in the construction and roading industries (best if olivine content is low); armour rock for seawalls; dimension stone, e.g. stone walls, curb stones, paving stones etc. composition= Basalt a mafic extrusive rock, is the most widespread of all igneous rocks, and comprises more than 90% of all volcanic rocks. Because of its relatively low silica content, basalt lava has a comparatively low viscosity, and forms thin flows that can travel long distances. It is also found as intrusive dikes and sills. Many moon rocks brought back by Apollo astronauts are of basaltic composition. Basalt is the volcanic equivalent of gabbro.

Travertine

white or light-colored calcareous rock deposited from mineral springs, used in building. Travertine is a natural stone such as Marble, Granite, Onyx, Limestone, Slate etc. The key difference between Travertine and other natural stones lies in the formation of the rock, the hardness of the stone and the appearance. Travertine is formed in hot springs and/or limestone caves. Travertine is not the same as Marble or Limestone which falls in the metamorphic rock category. Key characteristics of Travertine stone are the holes within the stone which are caused by carbon dioxide evasion. Environments of formation= Travertine is a form of limestone deposited by mineral springs, especially hot springs. Travertine often has a fibrous or concentric appearance and exists in white, tan, cream-colored, and even rusty varieties. It is formed by a process of rapid precipitation of calcium carbonate, often at the mouth of a hot spring or in a limestone cave. In the latter, it can form stalactites, stalagmites, and other speleothems. It is frequently used in Italy and elsewhere as a building material. Travertine is a terrestrial sedimentary rock, formed by the precipitation of carbonate minerals from solution in ground and surface waters, and/or geothermally heated hot-springs.[1][2] Similar (but softer and extremely porous) deposits formed from ambient-temperature water are known as tufa. SEDIMENTARY

Phyllite

-- a fine-grained metamorphic rock with a well-developed laminar structure, intermediate between slate and schist in degree of metamorphism. texture= Phyllite is from scientific Latin and means "leaf-stone." It's typically a medium-gray or greenish stone, but here sunlight reflects off its finely wavy face.Whereas slate has a dull surface because its metamorphic minerals are extremely fine grained, phyllite has a sheen from tiny grains of sericitic mica, graphite, chlorite and similar minerals, because with further heat and pressure, the reflective grains grow more abundant and join each other.And whereas slate usually breaks in very flat sheets, phyllite tends to have a corrugated cleavage.This rock has nearly all of its original sedimentary structure erased, although some of its clay minerals persist. Further metamorphism converts all of the clays into large grains of mica, along with quartz and feldspar. At that point, phyllite becomes schist. Environment of fromation= Shale is the parent rock. It is made up of clay minerals. Shale can metamorphose into slate, phyllite, schist or gneiss depending on the degree of heat and pressure. Phyllite has a greater degree of metamorphism than slate but less than schist. It tends to split easily and has a slightly corrugated surface along cleavage planes. It is associated with regional metamorphism due to mountain building. It is primarily composed of quartz, sericite mica, and chlorite.Phyllite has larger crystals than slate. This gives it a greater degree of light reflection or sheen. Slate is usually dull and non reflective.The sheen is used to distinguish phyllite from slate. Slates and phyllites typically form along the edges of regional metamorphic belts where clay-rich, marine sedimentary rocks have been caught between colliding continental plates, or scraped off the seafloor into an accretionary wedge above a subduction zone . Slates and phyllites may also form in sedimentary basins where marine muds have been extremely deeply buried. The assemblage of minerals usually present in phyllite is referred to as greenschist facies, and includes chlorite, muscovite, sodium-rich plagioclase feldspar , and a small amount of quartz . Greenschist metamorphism of shales requires moderate amounts of both heating and compression, consistent with the conditions present in accretionary wedges, shallow continental fold belts, and very deep sedimentary basins.Heating and compression of clay-rich, bedded sedimentary rocks called shales creates a series of rock types of increasing metamorphic grade: slate, phyllite, schist, and gneiss . During metamorphism of shales, and occasionally volcanic ash layers, metamorphism transforms platy clay minerals into small sheets of mica. As the intensity of heating and compression, the so-called metamorphic grade, increases, the mica sheets align themselves perpendicular to the direction of stress, and they grow larger. In phyllite, the crystals of sheet-silicate minerals like chlorite, biotite, and muscovite are large enough to give the rock its distinctive satin sheen and slaty cleavage, but not large enough to be visible to the unaided eye. The amount of heat and pressure required to transform shale to phyllite is generally sufficient to destroy any original sedimentary layering. Additional metamorphism transforms phyllite to schist; all the original clay and small mica crystals transform into large mica crystals, any remaining organic material is destroyed, and high-grade metamorphic index minerals like garnet and staurolite grow in the micaceous matrix. Grade of metamorphism= Phyllite is an intermediate-grade, foliated metamorphic rock type that resembles its sedimentary parent rock , shale, and its lower-grade metamorphic counterpart, slate . Like slate, phyllite can be distinguished from shale by its foliation, called slaty cleavage, and its brittleness, or fissility. Both slate and phyllite are generally dark-colored; their most common color is dark gray-blue, but dark red and green varieties also exist. Unlike slate, phyllite has a characteristic glossy sheen, its foliation is usually slightly contorted, and it rarely retains traces of the original sedimentary bedding . Phyllite also lacks the large, visible mica crystals and high-grade index minerals diagnostic of schist , its higher-grade metamorphic cousin.

Schist [mica]

--Schist is a foliated metamorphic rock made up of plate-shaped mineral grains that are large enough to see with an unaided eye. It usually forms on a continental side of a convergent plate boundary where sedimentary rocks, such as shales and mudstones, have been subjected to compressive forces, heat, and chemical activity. This metamorphic environment is intense enough to convert the clay minerals of the sedimentary rocks into platy metamorphic minerals such as muscovite, biotite, and chlorite. To become schist, a shale must be metamorphosed in steps through slate and then through phyllite. If the schist is metamorphosed further, it might become a granular rock known as gneiss. A rock does not need a specific mineral composition to be called "schist." It only needs to contain enough platy metamorphic minerals in alignment to exhibit distinct foliation. This texture allows the rock to be broken into thin slabs along the alignment direction of the platy mineral grains. This type of breakage is known as schistosity. In rare cases the platy metamorphic minerals are not derived from the clay minerals of a shale. The platy minerals can be graphite, talc, or hornblende from carbonaceous, basaltic, or other sources. Environments of formation= In the convergent plate boundary environment, heat and chemical activity transform the clay minerals of shales and mudstones into platy mica minerals such as muscovite, biotite, and chlorite. The directed pressure pushes the transforming clay minerals from their random orientations into a common parallel alignment where the long axes of the platy minerals are oriented perpendicular to the direction of the compressive force. This transformation of minerals marks the point in the rock's history when it is no longer sedimentary but becomes the low-grade metamorphic rock known as "slate." Slate is has a dull luster, it can be split into thin sheets along the parallel mineral alignments, and the thin sheets will ring when they are dropped onto a hard surface. If the slate is exposed to additional metamorphism, the mica grains in the rock will begin to grow. The grains will elongate in a direction that is perpendicular to the direction of compressive force. This alignment and increase in mica grain size gives the rock a silky luster. At that point the rock can be called a "phyllite." When the platy mineral grains have grown large enough to be seen with the unaided eye, the rock can be called "schist." Additional heat, pressure, and chemical activity might convert the schist into a granular metamorphic rock known as "gneiss." composition= as explained above, mica minerals such as chlorite, muscovite, and biotite are the characteristic minerals of schist. These were formed through metamorphism of the clay minerals present in the protolith. Other common minerals in schist include quartz and feldspars that are inherited from the protolith. Micas, feldspars, and quartz usually account for most of the minerals present in a schist. Schists are often named according to the eye-visible minerals of metamorphic origin that are obvious and abundant when the rock is examined. Muscovite schist, biotite schist, and chlorite schist (often called "greenstone") are commonly used names. Other names based upon obvious metamorphic minerals are garnetschist, kyanite schist, staurolite schist, hornblendeschist, and graphite schist. Some names used for schist often consist of three words, such as garnet graphite schist. In these cases the dominant metamorphic mineral's name is used second, and the less abundant mineral name is used first. Garnet graphite schist is a schist that contains graphite as its dominant mineral, but abundant garnet is visible and present. texture= For example, schists rich in mica are called mica schists and include biotite or muscovite. ... If the composition of the rocks was originally similar, they may be very difficult to distinguish from one another

Chalk

Chalk (pronunciation: /ˈtʃɔːk/) is a soft, white, porous sedimentary carbonate rock, a form of limestone composed of the mineral calcite. Calcite is an ionic salt called calcium carbonate or CaCO3. Environments of formation= Chalk rock (calcium carbonate), a pure form of limestone formed in warm, tropical seas about 100 million years ago in the Cretaceous Period when Dinosaurs ruled the Earth! Microscopic marine algae, called coccoliths, lived in the ancient sea. Their shells were made of calcite. As the algae died, their bodies sunk to the sea floor thus chalk sediment was deposited, so Chalk rock could be described as a "biological graveyard!" Over millions of years layers of chalk sediment were deposits caused compaction of loose sediment into solid chalk rock. Most limestones form in shallow, calm, warm marine waters. That type of environment is where organisms capable of forming calcium carbonate shells and skeletons can easily extract the needed ingredients from ocean water. When these animals die, their shell and skeletal debris accumulate as a sediment that might be lithified into limestone. Their waste products can also contribute to the sediment mass. Limestones formed from this type of sediment are biological sedimentary rocks. Their biological origin is often revealed in the rock by the presence of fossils. Some limestones can form by direct precipitation of calcium carbonate from marine or freshwater. Limestones formed this way are chemical sedimentary rocks. They are thought to be less abundant than biological limestones. Today Earth has many limestone-forming environments. Most of them are found in shallow water areas between 30 degrees north latitude and 30 degrees south latitude. Limestone is forming in the Caribbean Sea, Indian Ocean, Persian Gulf, Gulf of Mexico, around Pacific Ocean islands, and within the Indonesian archipelago. One of these areas is the Bahamas Platform, located in the Atlantic Ocean about 100 miles southeast of southern Florida (see satellite image). There, abundant corals, shellfish, algae, and other organisms produce vast amounts of calcium carbonate skeletal debris that completely blankets the platform. This is producing an extensive limestone deposit. Limestone can also form through evaporation. Stalactites, stalagmites, and other cave formations (often called "speleothems") are examples of limestone that formed through evaporation. In a cave, droplets of water seeping down from above enter the cave through fractures or other pore spaces in the cave ceiling. There they might evaporate before falling to the cave floor. When the water evaporates, any calcium carbonate that was dissolved in the water will be deposited on the cave ceiling. Over time, this evaporative process can result in an accumulation of icicle-shaped calcium carbonate on the cave ceiling. These deposits are known as stalactites. If the droplet falls to the floor and evaporates there, a stalagmite could grow upwards from the cave floor. The limestone that makes up these cave formations is known as "travertine" and is a chemical sedimentary rock. A rock known as "tufa" is a limestone formed by evaporation at a hot spring, lake shore, or other area. composition= Limestone is by definition a rock that contains at least 50% calcium carbonate in the form of calcite by weight. All limestones contain at least a few percent other materials. These can be small particles of quartz, feldspar, clay minerals, pyrite, siderite, and other minerals. It can also contain large nodules of chert, pyrite, or siderite. The calcium carbonate content of limestone gives it a property that is often used in rock identification - it effervesces in contact with a cold solution of 5% hydrochloric acid. There are many different names used for limestone. These names are based upon how the rock formed, its appearance or its composition, and other factors. Here are some of the more commonly used varieties. Chalk: A soft limestone with a very fine texture that is usually white or light gray in color. It is formed mainly from the calcareous shell remains of microscopic marine organisms such as foraminifers, or the calcareous remains from numerous types of marine algae. Coquina: A poorly-cemented limestone that is composed mainly of broken shell debris. It often forms on beaches where wave action segregates shell fragments of similar size. Fossiliferous Limestone: A limestone that contains obvious and abundant fossils. These are normally shell and skeletal fossils of the organisms that produced the limestone. Lithographic Limestone: A dense limestone with a very fine and very uniform grain size that occurs in thin beds which separate easily to form a very smooth surface. In the late 1700s, a printing process (lithography) was developed to reproduce images by drawing them on the stone with an oil-based ink and then using that stone to press multiple copies of the image. Oolitic Limestone: A limestone composed mainly of calcium carbonate "oolites," small spheres formed by the concentric precipitation of calcium carbonate on a sand grain or shell fragment. Travertine: A limestone that forms by evaporative precipitation, often in a cave, to produce formations such as stalactites, stalagmites, and flowstone. Tufa: A limestone produced by precipitation of calcium-laden waters at a hot spring, lake shore, or other location. texture= Chalk is a soft, white, porous sedimentary carbonate rock, a form of limestone composed of the mineral calcite. Calcite is an ionic salt called calcium carbonate

Diatomite

--Diatomite, also known as diatomaceous earth, is the naturally occurring fossilized remains of diatoms. Diatoms are single-celled aquatic algae. They belong to the class of golden brown algae known as Bacillariophyceae. Diatomite is a near pure sedimentary deposit consisting almost entirely of silica. The Greeks first used diatomite over 2,000 years ago in pottery and brick. There are many diatomite deposits throughout the world, but those of high-purity which are commercially viable are rare. The properties which make diatomite valuable include low density, high porosity, high surface area, abrasiveness, insulating properties, inertness, absorptive capacity, brightness, and high silica content. Diatomite has a wide variety of uses, and is a component in hundreds of products, or vital to the manufacturing process of thousands more. Filter Aids: The most important use relative of high-quality diatomite is as a filtering media. The naturally occurring fossilized remains of diatoms have innate filtering characteristics due to their unique honeycomb structure. Their filtering qualities are used in beer and wine making, pharmaceutical manufacturing, motor oil processing, and to filter swimming pool water. For almost 100 years diatomite has been the workhorse of food and beverage processing. Almost every shelf in the grocery store contains a product which has been filtered by diatomite. Functional Additives: In paints, diatomite alters glass and sheen, extends primary pigments, adds bulk and strength, controls permeability and enhances coating adhesion. In plastics, diatomite serves as an antiblocking agent which helps in the separation of plastic parts in manufacturing, and in the separation of plastic bags by the consumer. Absorbents: Due to such characteristics as porosity and high surface area, diatomite is highly absorbent and is very useful in the clean-up of spills in the automotive, industrial, janitorial and waste remediation industries. Soil Amendments: When diatomite is incorporated into soil, it serves to reduce compaction, and increase water and air permeation. It also increases plant available water, firms soggy soils, loosens hard to work soils, provides better drainage, aids in nutrient transfer, and improves root growth. In such applications as golf courses, and other landscaped areas it helps absorb and hold water, reducing the amount of water used. Natural Insecticide: When insects come in contact with diatomaceous earth, it absorbs their protective wax coating and their shells are damaged by the glassy diatoms. This combination causes them to die by dehydration. There is no survival and no built-up immunity as there is with chemical insecticides. Also, it does not break down as chemicals do. Diatomite is a friable light-colored sedimentary rock that is mainly composed of the siliceous skeletal remains of diatoms. It is a very porous rock with a fine particle size and a low specific gravity. These properties make it useful as a filter media, an absorbent, and as a lightweight filler for rubber, paint, and plastics. When diatomite is crushed into a powder, it is usually called "diatomaceous earth," or D.E. Diatoms are members of a large, diverse group of algae that drift freely in the waters of oceans and lakes. A few types of diatoms live on the bottom of these water bodies and in soils. Most diatoms are microscopic, but a few species are up to two millimeters in length. As a group, diatoms are unique because they are single-celled organisms that produce an external cell wall composed of silica, called a frustule. These frustules are very thin and have a delicate structure. Nearly all diatoms are photosynthetic and live in water less than about thirty feet deep, where sunlight can penetrate. Diatoms are prolific and are responsible for producing nearly half of the organic mass in the world's oceans. Their abundance and small size places them at the base of the marine food chain. Environments of formation= Diatomite forms in marine water and freshwater environments. These origins are an important consideration when a diatomite source is being considered for use. Any use that will be associated with human, animal, or plant contact should come from freshwater deposits. Diatomite from saltwater sources can contain salts that can produce objectionable or toxic effects. When diatoms die, their siliceous frustules sink. In some areas the frustules are not incorporated into the bottom sediment because they dissolve as they sink or dissolve while on the sediment surface. If the sediment is composed of over 30% diatom frustules by weight, it would be called a "diatom ooze" or a "siliceous ooze." These are the sediments that are lithified into the rock known as diatomite. composition= The typical chemical composition of oven-dried diatomaceous earth is 80 to 90% silica, with 2 to 4% alumina (attributed mostly to clay minerals) and 0.5 to 2% iron oxide. Diatomaceous earth consists of fossilized remains of diatoms, a type of hard-shelled protozoa. texture= Diatomite may resemble chalk or fine-grained volcanic ash beds. But pure diatomite is white or nearly white and quite soft, easy to scratch with a fingernail. When crumbled in water it may or may not turn gritty, but unlike degraded volcanic ash it doesn't turn slippery like clay. When tested with acid it will not fizz, unlike chalk. It is very lightweight and may even float on water. It can be dark if there is enough organic matter in it.

Conglomerate

--a coarse-grained sedimentary rock composed of rounded fragments (> 2 mm) within a matrix of finer grained material. Conglomerate is a clastic sedimentary rock that contains large (greater than two millimeters in diameter) rounded clasts. The space between the clasts is generally filled with smaller particles and/or a chemical cement that binds the rock together. composition= Conglomerate can have a variety of compositions. As a clastic sedimentary rock, it can contain clasts of any rock material or weathering product that is washed downstream or down current. The rounded clasts of conglomerate can be mineral particles such as quartz, or they can be sedimentary, metamorphic, or igneous rock fragments. The matrix that binds the large clasts together can be a mixture of sand, mud, and chemical cement. Conglomerate is a sedimentary rock made of rounded pebbles and sand that is usually held together (cemented) by silica, calcite or iron oxide. It is a stone similar to sandstone but the rock particles are rounded or angular gravel rather than sand. Environments of formation= Conglomerate forms where sediments of rounded clasts at least two millimeters in diameter accumulate. It takes a strong water current to transport and shape particles this large. So the environment of deposition might be along a swiftly flowing stream or a beach with strong waves. There must also be a source of large-size sediment particles somewhere up current. The rounded shape of the clasts reveals that they were tumbled by running water or moving waves. In September 2012, NASA's Mars rover Curiosity discovered an outcrop of conglomerate exposed on the surface of Mars. The rounded clasts within the conglomerate provide evidence that a stream or a beach had moved the rocks and tumbled them into rounded pebbles. This conglomerate was the most convincing evidence that water once flowed on the surface of Mars. Conglomerates often begin by being deposited as a sediment consisting mainly of pebble and cobble-size clasts. The finer-size sand and clay, which fill the spaces between the larger clasts, is often deposited layer on top of the large clasts and then sifts down between them to fill the interstitial spaces. The deposition of a chemical cement then binds the sediment into a rock. uses= Conglomerate has very few commercial uses. Its inability to break cleanly makes it a poor candidate for dimension stone, and its variable composition makes it a rock of unreliable physical strength and durability. Conglomerate can be crushed to make a fine aggregate that can be used where a low-performance material is suitable. Many conglomerates are colorful and attractive rocks, but they are only rarely used as an ornamental stone for interior use. Analysis of conglomerate can sometimes be used as a prospecting tool. For example, most diamond deposits are hosted in kimberlite. If a conglomerate contains clasts of kimberlite, then the source of that kimberlite must be somewhere upstream. texture= Conglomerate (pronunciation: /kəŋˈɡlɒmərᵻt/) is a coarse-grained clastic sedimentary rock that is composed of a substantial fraction of rounded to subangular gravel-size clasts, e.g., granules, pebbles, cobbles, and boulders, larger than 2 mm (0.079 in) in diameter. There are three basic types of sedimentary rocks: 1) clastic sedimentary rockssuch as breccia, conglomerate, sandstone and shale, that are formed from mechanical weathering debris; 2) chemical sedimentary rocks such as rock salt and some limestones, that form when dissolved materials precipitate from solution; Breccia and conglomerate are very similar rocks. They are both clastic sedimentary rocks composed of particles larger than two millimeters in diameter. The difference is in the shape of the large particles. In breccia the large particles are angular in shape but in conglomerate the particles are rounded.

Ulexite

Chemical formula= NaCaB5O9 · 8H2O composition= Hydrous sodium calcium borate color=white to light gray Streak = white hardness= 2.5 Crystal system= triclinic Crystal form= Rarely in noticeable crystals; occurs in groups of tiny crystals in rounded or lenticular aggregates. It is most commonly seen as compact, parallel, fibrous veins. Also occasionally encrusting and as radial compactions of thin crystals .transparency= Transparent to translucent gravity= 1.6-1.9 luster= silky cleavage= 1,1 - prismatic ; 2,1 - basal fracture= Uneven to splintery tenacity= brittle

Almandine

Silicates. Garnet group. transparency= transparent to opaque Crystal system= cubic composition=iron aluminium silicate (iron can be replaced by magnesium or manganese streak= colorless Crystal forms= Crystals may be striated or with stepped growth layers, and are sometimes warped into rounded ball-like forms. Also in dodecahedral crystal aggregates, grainy, massive, and as rounded waterworn crystals. luster= vitreous cleavage= none- may exhibit parting tenacity= brittle fracture= conchoidal to uneven group= silicates, nesosilicates, garnet

Jasper

Variety of Quartz Composition: Silicon dioxide, usually with impurities of iron oxides or organic substances. Color: Brown, yellow, orange, red, green, or blue. May also refer to any form of opaque Chalcedony in all colors. Is usually multicolored or banded. Streak: White Crystal System: Hexagonal Crystal Forms and Aggregates: is a microcrystalline form of the mineral Quartz, and does not occur in visible crystals. It most often is in massive form, but may also be botryoidal, mammillary, and stalactitic formations, as smooth rounded pebbles, and as nodules. Transparency: Opaque Luster: Vitreous Cleavage: None Fracture: Conchoidal Tenacity: Brittle

Halite

composition= sodium chloride color= Colorless, white, red, yellow, orange, pink, blue, violet, green, and gray. May also be multicolored with a solid and clear color such as blue and white. streak= white Crystal system= isometric Crystal forms= Crystals occur as cubes, sometimes distorted with hopper growths. Rarely occurs octahedral. Normally occurs massive, grainy, encrusting, as fibrous veins, botryoidal, stalactitic. Large cubic chunks often break apart into cubic cleavage fragments. Also forms as odd shaped rectangular crystal clusters and elongated scepters of cubic crystals. transparency= transparent to translucent luster=vitreous cleavage= 1,all sides - cubic fracture= conchoidal tenacity= brittle

Slate

--a fine-grained gray, green, or bluish metamorphic rock easily split into smooth, flat pieces. composition= Slate is composed mainly of clay minerals or micas, depending upon the degree of metamorphism to which it has been subjected. The original clay minerals in shale alter to micas with increasing levels of heat and pressure. Slate can also contain abundant quartz and small amounts of feldspar, calcite, pyrite, hematite, and other minerals. Environments in formation= The tectonic environment for producing slate is usually a former sedimentary basin that becomes involved in a convergent plate boundary. Shales and mudstones in that basin are compressed by horizontal forces with minor heating. These forces and heat modify the clay minerals in the shale and mudstone. Foliation develops at right angles to the compressive forces of the convergent plate boundary to yield a vertical foliation that usually crosses the bedding planes that existed in the shale. //Most of the slate mined throughout the world is used to produce roofing slates. Slate performs well in this application because it can be cut into thin sheets, absorbs minimal moisture, and stands up well in contact with freezing water. A disadvantage is the cost of the slate and its installation in comparison with other roofing materials. As a result, in new construction slate is mainly confined to high-end projects and prestige architecture. Slate is also used for interior flooring, exterior paving, dimension stone, and decorative aggregate. Small pieces of slate are also used to make turkey calls. The photos on this page document several uses of slate. Historically slate has been used for chalkboards, student writing slates, billiard tables, cemetery markers, whetstones, and table tops. Because it is a good electrical insulator, it was also used for early electric panels and switch boxes. texture=s late is a fine-grain, foliated metamorphic rock formed under extreme pressure and heat conditions from sedimentary rocks such as shale, clay or ash. Grade of metamorphism= Slate is a low grade metamorphic rock generally formed by the metamorphosis of mudstone / shale, or sometimes basalt, under relatively low pressure and temperature conditions. Clay minerals in the parent rock metamorphose into mica minerals (biotote, chlorite, muscovite) which are aligned along foliation planes perpendicular to the direction of pressure. Slate is characterized by fine foliation along which it breaks to leave smooth, flat surfaces (often referred to as "slaty cleavage" - not to be confused with cleavage in minerals). Sometimes relict (original) bedding is visible on foliation planes. Slate will 'ring' when struck, unlike mudstone or shale which makes a dull 'thud'. Phyllite, a metamorphic rock very similar to slate, has undergone a slightly greater degree of metamorphism. It is slightly coarser-grained (some crystals may be visible to the naked eye), and the foliation is less perfect (it lacks perfect "slaty cleavage"). Texture - foliated, foliation on a mm scale. Grain size - very fine-grained; crystals not visible to the naked eye. Hardness - hard and brittle. Colour - variable - black, shades of blue, green, red, brown and buff. Mineralogy - contains mica minerals (biotite, chlorite, muscovite) which typically impart a sheen on foliation surfaces; can contain cubic pyrite porphyroblasts. Other features - smooth to touch. Uses - historically extensively used for roof and floor tiles, and blackboards; standard material for the beds of pool / snooker / billiard tables. New Zealand occurrences - northwest Nelson

Lepidolite

Composition: Basic potassium lithium aluminum fluorosilicate Color: Pink to purple. Occasionally also light gray and yellow. Streak: White Crystal system: Monoclinic Crystal Forms and Aggregates: Most often as small, scaly crystals in dense aggregates. Also as micaceous masses and groupings, and in tabular, foliated, flaky, and scaly forms. Large crystals, which are in stubby pseudohexagonal form, are much rarer then the other micas. Also found in micaceous rounded ball-shaped aggregates and in massive form with tiny glittery crystals. Transparency: Transparent to translucent Luster: Pearly Cleavage: 1,1 Fracture: Uneven Tenacity: Sectile, Elastic

Arkose

--Arkose (pronunciation: /ˈɑːrkoʊz/) is a detrital sedimentary rock, specifically a type of sandstone containing at least 25% feldspar. Arkosic sand is sand that is similarly rich in feldspar, and thus the potential precursor of arkose. Quartz is commonly the dominant mineral component, and some mica is often present. composition= Arkose is known to be young because of its content of feldspar, a mineral that usually degrades quickly into clay. Its mineral grains are generally angular rather than smooth and rounded, another sign that they were transported only a short distance from their origin. Arkose usually has a reddish color from feldspar, clay and iron oxides—ingredients that are uncommon in ordinary sandstone. Environments of formation= The grains of sand in a sandstone are usually particles of mineral, rock, or organic material that have been reduced to "sand" size by weathering and transported to their depositional site by the action of moving water, wind, or ice. Their time and distance of transport may be brief or significant, and during that journey the grains are acted upon by chemical and physical weathering. If the sand is deposited close to its source rock, it will resemble the source rock in composition. However, the more time and distance that separate the source rock from the sand deposit, the greater its composition will change during transport. Grains that are composed of easily-weathered materials will be modified, and grains that are physically weak will be reduced in size or destroyed. If a granite outcrop is the source of the sand, the original material might be composed of grains of hornblende, biotite, orthoclase, and quartz. Hornblende and biotite are the most chemically and physically susceptible to destruction, and they would be eliminated in the early stage of transport. Orthoclase and quartz would persist longer, but the grains of quartz would have the greatest chance of survival. They are more chemically inert, harder, and not prone to cleavage. Quartz is typically the most abundant type of sand grain present in sandstone. It is extremely abundant in source materials and is extremely durable during transport. texture= Arkose. Arkose is a feldspar-rich sandstone. It is commonly coarse-grained and usually either pink or gray (depending on the color of feldspar). Arkose is a type of sandstone that contains lots of feldspar grains.

Granite

--Granite is a light-colored igneous rock with grains large enough to be visible with the unaided eye. It forms from the slow crystallization of magma below Earth's surface. Granite is composed mainly of quartz and feldspar with minor amounts of mica, amphiboles, and other minerals. This mineral composition usually gives granite a red, pink, gray, or white color with dark mineral grains visible throughout the rock. Environments of formation= Most introductory geology textbooks report that granite is the most abundant rock in the continental crust. At the surface, granite is exposed in the cores of many mountain ranges within large areas known as "batholiths," and in the core areas of continents known as "shields." The large mineral crystals in granite are evidence that it cooled slowly from molten rock material. That slow cooling had to have occurred beneath Earth's surface and required a long period of time to occur. If they are today exposed at the surface, the only way that could happen is if the granite rocks were uplifted and the overlying sedimentary rocks were eroded. In areas where Earth's surface is covered with sedimentary rocks, granites, metamorphosed granites, or closely related rocks are usually present beneath the sedimentary cover. These deep granites are known as "basement rocks." texture= Some granites are foliated. Granite also tends to have coarse intergrowths of feldspars and quartz that form a graphic texture. It has colorless grains, and it is mottled in white, red, pink, grey or dark grains. It is classified as acid plutonic igneous rock, composition= Granite is composed mainly of quartz and feldspar with minor amounts of mica, amphiboles, and other minerals. This mineral composition usually gives granite a red, pink, gray, or white color with dark mineral grains visible throughout the rock. formation= Granite is found in large plutons on the continents, in areas where the Earth's crust has been deeply eroded. This makes sense, because granite must cool very slowly at deeply buried locations to produce such large mineral grains. Plutons smaller than 100 square kilometers in area are called stocks, and larger ones are called batholiths. Lavas erupt all over the Earth, but lava with the same composition as granite (rhyolite) only erupts on the continents. That means that granite must form by the melting of continental rocks. That happens for two reasons: adding heat and adding volatiles (water or carbon dioxide or both). Continents are relatively hot because they contain most of the planet's uranium and potassium, which heat up their surroundings through radioactive decay. Anywhere that the crust is thickened tends to get hot inside (for instance in the Tibetan Plateau). And the processes of plate tectonics, mainly subduction, can cause basaltic magmas to rise underneath the continents. In addition to heat, these magmas release CO2 and water, which helps rocks of all kinds melt at lower temperatures. It is thought that large amounts of basaltic magma can be plastered to the bottom of a continent in a process called underplating. With the slow release of heat and fluids from that basalt, a large amount of continental crust could turn to granite at the same time.

Rhyolite

--Rhyolite is an igneous, volcanic rock, of felsic (silica-rich) composition (typically > 69% SiO2—see the TAS classification). It may have any texture from glassy to aphanitic to porphyritic. Group - volcanic. Colour - variable, but light coloured. Texture - usually porphyritic, but can be aphanitic (e.g. obsidian). Mineral content - groundmass generally of quartz and plagioclase, with lesser amounts of orthoclase, biotite, amphibole (augite), pyroxene (hornblende), and glass; phenocrysts of plagioclase and quartz, often with amphibole and / or biotite, sometimes orthoclase. Silica (SiO2) content - 69%-77%. Uses - can be used as aggregate, fill etc. in the construction and roading industries (often not ideal for concrete aggregate because of high silica content); obsidian was used by pre-European Maori as a cutting tool, and can be carved into jewellery; pumice is used as an abrasive (especially in the cosmetic industry), and can also be incorporated into lightweight building materials. Rhyolite is a felsic extrusive rock. Due to the high silica content, rhyolite lava is very viscous. It flows slowly, like tooth paste squeezed out of a tube, and tends to pile up and form lava domes. If rhyolite magma is gas rich it can erupt explosively, forming a frothy solidified magma called pumice (a very lightweight, light-coloured, vesicular form of rhyolite) along with ash deposits, and / or ignimbrite. In certain situations extremely porous rhyolite lava flows may develop. The extreme porosity of such flows allows degassing and subsequent collapse of the flow, forming obsidian (dark coloured volcanic glass). Rhyolite is the volcanic equivalent of granite. Environments of formation= Rhyolite is an extrusive igneous rock with a very high silica content. It is usually pink or gray in color with grains so small that they are difficult to observe without a hand lens. Rhyolite is made up of quartz, plagioclase, and sanidine, with minor amounts of hornblende and biotite. Trapped gases often produce vugs in the rock. These often contain crystals, opal, or glassy material. Many rhyolites form from granitic magma that has partially cooled in the subsurface. When these magmas erupt, a rock with two grain sizes can form. The large crystals that formed beneath the surface are called phenocrysts, and the small crystals formed at the surface are called groundmass. Rhyolite usually forms in continental or continental-margin volcanic eruptions where granitic magma reaches the surface. Rhyolite is rarely produced at oceanic eruptions. composition= Rhyolite is an extrusive igneous rock with a very high silica content. It is usually pink or gray in color with grains so small that they are difficult to observe without a hand lens. Rhyolite is made up of quartz, plagioclase, and sanidine, with minor amounts of hornblende and biotite.

Scoria

--a cindery, vesicular basaltic lava, typically having a frothy texture. //Scoria is a dark-colored igneous rock with abundant round bubble-like cavities known as vesicles. It ranges in color from black or dark gray to deep reddish brown. Scoria usually has a composition similar to basalt, but it can also have a composition similar to andesite. Many people believe that small pieces of scoria look like the ash produced in a coal furnace. That has resulted in particles of scoria being called "cinders" and the small volcanoes that erupt scoria to be called "cinder cones." Environments of formation= Scoria forms when magma containing abundant dissolved gas flows from a volcano or is blown out during an eruption. As the molten rock emerges from the Earth, the pressure upon it is reduced and the dissolved gas starts to escape in the form of bubbles. If the molten rock solidifies before the gas has escaped, the bubbles become small rounded or elongated cavities in the rock. This dark-colored igneous rock with the trapped bubbles is known as scoria. When some volcanoes erupt, a rush of gas blows out of the vent. This gas was once dissolved in the magma below. The gas often blows out small bodies of magma that solidify as they fly through the air. This action can produce a ground cover of scoria all around the volcanic vent, with the heaviest deposits on the downwind side. Small particles of scoria that litter the landscape around the volcano are known as "lapilli" if they are between 2 millimeters and 64 millimeters in size. Larger particles are known as "blocks." //it also is blown out of the crater during eruptions. Unlike pumice, scoria usually has broken, connected bubbles and does not float in water. texture= Scoria is a highly vesicular, dark colored volcanic rock that may or may not contain crystals (phenocrysts). It is typically dark in color (generally dark brown, black or purplish red), and basaltic or andesitic in composition.

Pegmatite

--a coarsely crystalline granite or other igneous rock with crystals several centimeters to several meters in length //Pegmatites are extreme igneous rocks that form during the final stage of a magma's crystallization. They are extreme because they contain exceptionally large crystals and they sometimes contain minerals that are rarely found in other types of rocks. To be called a "pegmatite," a rock should be composed almost entirely of crystals that are at least one centimeter in diameter. The name "pegmatite" has nothing to do with the mineral composition of the rock. Most pegmatites have a composition that is similar to granite with abundant quartz, feldspar, and mica. These are sometimes called "granite pegmatites" to indicate their mineralogical composition. However, compositions such as "gabbro pegmatite," "syenite pegmatite," and any other plutonic rock name combined with "pegmatite" are possible. Pegmatites are sometimes sources of valuable minerals such as spodumene (an ore of lithium) and beryl (an ore of beryllium) that are rarely found in economic amounts in other types of rocks. They also can be a source of gemstones. Some of the world's best tourmaline, aquamarine, and topaz deposits have been found in pegmatites. texture= Pegmatitic Textures. A pegmatitic texture is one in which the mineral grains are exceptionally large. The largest ones are, by convention, more than about 3 cm long. This texture is found in intrusive rocks. ... Instead, the large crystals of a pegmatite formed in a magma that was extra rich in dissolved water.

Diamond

Chemical formula= C composition= carbon color= Colorless, white, yellow, and brown, gray, and black. Colorless ones are usually lightly tinged with yellow, orange or brown. Rarely blue, green, red, orange, pink, or purple. streak= white Crystal system= isometric Crystal forms= Most often octahedral, frequently with many crystal faces. Dodecahedral and hexoctahedral crystals, although less common, also occur. Cubic crystals are rare. Crystals may often contain complex growth layers or triangular features known as "trigons". Also forms in twinned crystals, and as both clean cleavage fragments and unshaped distorted fragments. Some twinned crystals and cleavage fragments assume a triangular shape, which are known as macles. Crystals often have curved faces, and in some cases they be almost round. Another crystal habit is ball-shaped agglomerates of radiating crystals. Also occurs fibrous, massive and as severely distorted crystals. transparency= transparent to opaque luster= Adamantine. Rough stones have a greasy luster. cleavage= 1, all sides - octahedral. Dodecahedral, Borts, and Carbonado exhibit poor or no cleavage. fracture= conchoidal tenacity= brittle

Gabbro

--a dark, coarse-grained plutonic rock of crystalline texture, consisting mainly of pyroxene, plagioclase feldspar, and often olivine. //Gabbro is a coarse-grained, dark-colored, intrusive igneous rock. It is usually black or dark green in color and composed mainly of the minerals plagioclase and augite. It is the most abundant rock in the deep oceanic crust. Gabbro has a variety of uses in the construction industry. It is used for everything from crushed stone base materials at construction sites to polished stone counter tops and floor tiles. composition=Gabbro is composed mainly of calcium-rich plagioclase feldspar (usually labradorite or bytownite) and clinopyroxene (augite). Minor amounts of olivine and orthopyroxene might also be present in the rock. (See composition chart on this page.) This mineral composition usually gives gabbro a black to very dark green color. A minor amount of light-colored mineral grains may also be present. Unlike many other igneous rocks, gabbro usually contains very little quartz. environment= It is often stated that Earth's oceanic crust is made up of basalt. The word "basalt" is used because the rocks of the oceanic crust have a "basaltic" composition. However, only a thin surface veneer of oceanic crust is basalt. The deeper rocks of the oceanic crust are generally coarser-grained gabbro. Basalt occurs at the surface of the crust because the rocks there have cooled quickly. At greater depth the cooling rate is slower, and large crystals have time to develop. On the continents, gabbro can be found within thick lava flows of basaltic composition, where slow cooling allows large crystals to form. Gabbro will also be present in the deep plutons that form when magma chambers that feed basaltic eruptions crystallize. --Gabbro can be polished to a brilliant black luster. Brightly polished gabbro is used to make cemetery markers, kitchen counter tops, floor tiles, facing stone, and other dimension stone products. It is a highly desirable rock that stands up to weathering and wear. In the dimension stone industry, gabbro is sold under the name "black granite." Gabbro is also used to make a number of rough-cut products such as curbing, ashlars, paving stones, and other products. The most common use of gabbro is as a crushed stone or aggregate. Crushed gabbro is used as a base material in construction projects, as a crushed stone for road construction, as railroad ballast, and anywhere that a durable crushed stone is needed as fill.

Obsidian

--a hard, dark, glasslike volcanic rock formed by the rapid solidification of lava without crystallization. obsidian is a naturally occurring volcanic glass formed as an extrusive igneous rock. It is produced when felsic lava extruded from a volcano cools rapidly with minimal crystal growth. location= Obsidian is usually an extrusive rock - one that solidifies above Earth's surface. However, it can form in a variety of cooling environments: along the edges of a lava flow (extrusive), along the edges of a volcanic dome (extrusive), around the edges of a sill or a dike (intrusive), where lava contacts water (extrusive), where lava cools while airborne (extrusive) //Obsidian is found in many locations worldwide. It is confined to areas of geologically recent volcanic activity. Obsidian older than a few million years is rare because the glassy rock is rapidly destroyed or altered by weathering, heat, or other processes. ;;Although using a rock as a cutting tool might sound like "stone age equipment," obsidian continues to play an important role in modern surgery. Obsidian can be used to produce a cutting edge that is thinner and sharper than the best surgical steel. Today, thin blades of obsidian are placed in surgical scalpels used for some of the most precise surgery. In controlled studies, the performance of obsidian blades was equal to or superior to the performance of surgical steel. texture= A hand specimen of obsidian(volcanic glass). The cooling occurs so rapidly that no crystals have time to form. Thus, we have a glass (no ordering like in minerals) and the rock breaks like glass does, with a conchoidal fracture. composition= t is sometimes classified as a mineraloid. Though obsidian is usually dark in color similar to mafic rocks such as basalt, obsidian's composition is extremely felsic. Obsidian consists mainly of SiO2 (silicon dioxide), usually 70% or more. Crystalline rocks with obsidian's composition include granite and rhyolite.

Gneiss

--a metamorphic rock with a banded or foliated structure, typically coarse-grained and consisting mainly of feldspar, quartz, and mica. composition= Although gneiss is not defined by its composition, most specimens have bands of feldspar and quartz grains in an interlocking texture. These bands are usually light in color and alternate with bands of darker-colored minerals with platy or elongate habits. The dark minerals sometimes exhibit an orientation determined by the pressures of metamorphism. Some specimens of gneiss contain distinctive minerals characteristic of the metamorphic environment. These minerals might include biotite, cordierite, sillimanite, kyanite, staurolite, andalusite, and garnet. Gneiss is sometimes named for these minerals, examples of which include "garnet gneiss" and "biotite gneiss." Environments of formation= Gneiss is a high grade metamorphic rock, meaning that it has been subjected to higher temperatures and pressures than schist. It is formed by the metamorphosis of granite, or sedimentary rock. Gneiss displays distinct foliation, representing alternating layers composed of different minerals. However, unlike slate and schist, gneiss does not preferentially break along planes of foliation because less than 50% of the minerals formed during the metamorphism are aligned in thin layers. Because of the coarseness of the foliation, the layers are often sub-parallel, i.e. they do not have a constant thickness, and discontinuous. Gneiss is typically associated with major mountain building episodes. During these episodes, sedimentary or felsic igneous rocks are subjected to great pressures and temperatures generated by great depth of burial, proximity to igneous intrusions and the tectonic forces generated during such episodes. Gneisses from western Greenland comprise the oldest crustal rocks known (more than 3.5 billion years old). Gneiss is an old German word meaning bright or sparkling. Grade of metamorphism= high grade

Lignite

--a soft brownish coal showing traces of plant structure, intermediate between bituminous coal and peat. Variety of coal Lignite coal is the lowest grade of coal and is brownish-black in appearance. Coal forms from organic carbon in plant material like peat. As the peat is squeezed at low temperatures, lignite rocks forms as a results. Sometimes called "Jet," this sedimentary rock is used a gemstone and a fuel. An information card with details on the rocks formation, mineral content, characteristics and uses is included. Typical samples sizes are generally 1-2 inches in length or width but can vary based on availability and natural formation. Lignite, often referred to as brown coal, is a soft brown combustible sedimentary rock formed from naturally compressed peat. It is considered the lowest rank of coal due to its relatively low heat content. texture= Veined or Pebbled

Diorite

--a speckled, coarse-grained igneous rock consisting essentially of plagioclase, feldspar, and hornblende or other mafic minerals. --Diorite is the name used for a group of coarse-grained igneous rocks with a composition between that of granite and basalt. It usually occurs as large intrusions, dikes, and sills within continental crust. These often form above a convergent plate boundary where an oceanic plate subducts beneath a continental plate. Partial melting of the oceanic plate produces a basaltic magma that rises and intrudes the granitic rock of the continental plate. There, the basaltic magma mixes with granitic magmas or melts granitic rock as it ascends through the continental plate. This produces a melt that is intermediate in composition between basalt and granite. Diorite forms if this type of melt crystallizes below the surface. Diorite is usually composed of sodium-rich plagioclase with lesser amounts of hornblende and biotite. It usually contains little if any quartz. This makes diorite a coarse-grained rock with a contrasting mix of black and white mineral grains. Students often use this "salt and pepper" appearance as a clue to the identification of diorite. //Diorite and andesite are similar rocks. They have the same mineral composition and occur in the same geographic areas. The differences are in their grain sizes and their rates of cooling. Diorite crystallized slowly within the Earth. That slow cooling produced a coarse grain size. Andesite forms when a similar magma crystallizes quickly at Earth's surface. That rapid cooling produces a rock with small crystals. composition= Being of intermediate composition between felsic and mafic, diorite is classically a salt and pepper rock made largely of white to light gray plagioclase and black hornblende. Some diorites contain biotite as well as hornblende, and some contain up to 10% quartz. If you have more than 10% quartz, you probably have a granite on your hands. If you clearly have abundant K-feldspar, you probably have a granite on your hands.

Malachite

Composition: Basic copper carbonate Color: Light to dark green, sometimes banded with darker and lighter shades of green, and sometimes sparkling. Streak: Light green Crystal system: Monoclinic Crystal forms and aggregates: Most common habit is as large crusts of microscopic crystals. Also occurs as bundles of thin long splinters. Large individual crystals are very rare and are usually pseudomorphs after Azurite or Cuprite. When they are not pseudomorphs, they are prismatic, tabular, re-entrant twins, and thin splinters. Also occurs acicular, radiating, reniform, botryoidal, as banded masses, earthy, stalactitic,tuberose, as thin wires, and as thin films coating other minerals. Transparency: Opaque, although translucent in thin splinters Luster: Vitreous, silky, or dull Cleavage: 1,1 - basal. Not usually discernible because crystals are tiny. Fracture: Splintery Tenacity: Brittle

Pumice

--a very light and porous volcanic rock formed when a gas-rich froth of glassy lava solidifies rapidly. Pumice is a light-colored, extremely porous igneous rock that forms during explosive volcanic eruptions. It is used as aggregate in lightweight concrete, as landscaping aggregate, and as an abrasive in a variety of industrial and consumer products. Many specimens have a high enough porosity that they can float on water until they slowly become waterlogged. Environments of formation= the pore spaces (known as vesicles) in pumice are a clue to how it forms. The vesicles are actually gas bubbles that were trapped in the rock during the rapid cooling of a gas-rich frothy magma. The material cools so quickly that atoms in the melt are not able to arrange themselves into a crystalline structure. Thus, pumice is an amorphous volcanic glass known as a "mineraloid." Some magmas contain several percent dissolved gas by weight while they are under pressure. Stop for a moment and think about that. Gas weighs very little at Earth's surface, but these magmas under pressure can contain several percent gas by weight held in solution. This is similar to the large amount of dissolved carbon dioxide in a sealed bottle of carbonated beverage such as beer or soda. If you shake the container, then immediately open the bottle, the sudden release of pressure allows the gas to come out of solution, and the beverage erupts from the container in a frothy mess. A rising body of magma, supercharged with dissolved gas under pressure, behaves in a similar way. As the magma breaks through Earth's surface, the sudden pressure drop causes the gas to come out of solution. This is what produces the enormous rush of high-pressure gas from the vent. This rush of gas from the vent shreds the magma and blows it out as a molten froth. The froth rapidly solidifies as it flies through the air and falls back to Earth as pieces of pumice. The largest volcanic eruptions can eject many cubic kilometers of material. This material can range in size from tiny dust particles to large blocks of pumice the size of a house. Large eruptions can blanket the landscape around the volcano with over 100 meters of pumice and launch dust and ash high into the atmosphere. composition= Most pumice erupts from magmas that are highly charged with gas and have a rhyolitic composition. Rarely, pumice can erupt from gas-charged magmas of basaltic or andesitic composition. ;;The abundant vesicles in pumice and the thin walls between them give the rock a very low specific gravity. It typically has a specific gravity of less than one, giving the rock an ability to float on water. texture= Pumice (pronunciation: /ˈpʌmᵻs/), called pumicite in its powdered or dust form, is a volcanic rock that consists of highly vesicular rough textured volcanic glass, which may or may not contain crystals. It is typically light colored.

Quartzite

--an extremely compact, hard, granular rock consisting essentially of quartz. It often occurs as silicified sandstone, as in sarsen stones. //Quartzite is usually white to gray in color. Some rock units that are stained by iron can be pink, red, or purple. Other impurities can cause quartzite to be yellow, orange, brown, green, or blue. The quartz content of quartzite gives it a hardness of about seven on the Mohs Hardness Scale. Its extreme toughness made it a favorite rock for use as an impact tool by early people. Its conchoidal fracture allowed it to be shaped into large cutting tools such as ax heads and scrapers. Its coarse texture made it less suitable for producing tools with fine edges such as knife blades and projectile points. Environments in formation= Most quartzite forms during mountain-building events at convergent plate boundaries. There, sandstone is metamorphosed into quartzite while deeply buried. Compressional forces at the plate boundary fold and fault the rocks and thicken the crust into a mountain range. Quartzite is an important rock type in folded mountain ranges throughout the world. When the mountain ranges are worn down by weathering and erosion, less-resistant and less-durable rocks are destroyed, but the quartzite remains. This is why quartzite is so often the rock found at the crests of mountain ranges and covering their flanks as a litter of scree. Quartzite is also a poor soil-former. Unlike feldspars which break down to form clay minerals, the weathering debris of quartzite is quartz. It is therefore not a rock type that contributes well to soil formation. For that reason it is often found as exposed bedrock with little or no soil cover. composition= The interlocking crystalline structure of quartzite makes it a hard, tough, durable rock. It is so tough that it breaks through the quartz grains rather than breaking along the boundaries between them. This is a characteristic that separates true quartzite from sandstone. Texture- foliated and granular uses= Quartzite has a diversity of uses in construction, manufacturing, architecture, and decorative arts. Although its properties are superior to many currently used materials, its consumption has always been low for various reasons. gom = Rock is medium to coarse grained with visible grains of mica or other metamorphic minerals. Often shiny due to reflection of mica on foliation planes. Product of intermediate grade metamorphism of shale, slate, phyllite, basalt or granite.

Dolostone

--rock consisting of dolomite. -- Dolomite, also known as "dolostone" and "dolomite rock," is a sedimentary rock composed primarily of the mineral dolomite, CaMg(CO3)2. Dolomite is found in sedimentary basins worldwide. It is thought to form by the post depositional alteration of lime mud and limestone by magnesium-rich groundwater. Dolomite and limestone are very similar rocks. They share the same color ranges of white-to-gray and white-to-light brown (although other colors such as red, green, and black are possible). They are approximately the same hardness, and they are both soluble in dilute hydrochloric acid. They are both crushed and cut for use as construction materials and used for their ability to neutralize acids. Environments of formation= Dolomite is very common in the rock record, but the mineral dolomite is rarely observed forming in sedimentary environments. For this reason it is believed that most dolomites form when lime muds or limestones are modified by post depositional chemical change. Dolomite originates in the same sedimentary environments as limestone - warm, shallow, marine environments where calcium carbonate mud accumulates in the form of shell debris, fecal material, coral fragments, and carbonate precipitates. Dolomite is thought to form when the calcite (CaCO3) in carbonate mud or limestone is modified by magnesium-rich groundwater. The available magnesium facilitates the conversion of calcite into dolomite (CaMg(CO3)2). This chemical change is known as "dolomitization." Dolomitization can completely alter a limestone into a dolomite, or it can partially alter the rock to form a "dolomitic limestone." Dolomite is slightly harder than limestone. Dolomite has a Mohs hardness of 3.5 to 4, and limestone (composed of the mineral calcite) has a hardness of 3. Dolomite is slightly less soluble in dilute hydrochloric acid. Calcite will effervesce vigorously in contact with cold, dilute (5%) hydrochloric acid, while dolomite produces a very weak effervescence. These differences are often not significant enough to make a positive identification in the field. Distinguishing the rocks in the field is further complicated by a compositional continuum that ranges from limestone to dolomitic limestone to dolomite. A chemical analysis that determines the relative abundances of calcium and magnesium is needed to accurately name the rocks. //Dolomite behaves like limestone when it is subjected to heat and pressure. It begins to recrystallize as the temperature rises. As this occurs, the size of the dolomite crystals in the rock increases, and the rock develops a distinctly crystalline appearance If you examine the photo of granular dolomite, you will see that the rock is composed of easily recognizable dolomite crystals. The coarse crystalline texture is a sign of recrystallization, most often caused by metamorphism. Dolomite that has been transformed into a metamorphic rock is called "dolomitic marble." Dolomite is a common rock-forming mineral. It is a calcium magnesium carbonate with a chemical composition of CaMg(CO3)2. It is the primary component of the sedimentary rock known as dolostone and the metamorphic rock known as dolomitic marble. texture= Nonclastic; Very Fine-grained. It's a sedimentary rock but when it is turned into dolomite marble it has a low grade of metamorphism.

Calcite

Chemical composition= Calcium carbonate, sometimes with impurities of iron, magnesium, or manganese, and occasionally zinc and cobalt. color= Colorless, white, yellow, brown, orange, pink, red, purple, blue, green, gray, black. May also be multicolored or banded. streak= white Crystal system= hexagonal Crystal form- Occurs in a great variety of shapes, with the most common forms as rhombohedral and scalenohedral crystals. Crystals may be tabular, acicular, prismatic, flaky, and needle-like. May occur as bundles of scalenohedral, intergrown rhombohedrons, hair-like masses of acicular crystals, grainy, stalactitic, fibrous, massive, and earthy. Scalenohedral twinning is common. Transparency = transparent to opaque luster= vitreous cleavage= 1,3, rhombohedral fracture= conchoidal. Rarely observed due to the perfect cleavage. tenacity= brittle

Barite

Chemical composition= barium sulfate, sometimes with small amounts of strontium. color= colorless, white, yellow, green, pink ,purple,blue orange, red,brown, gray, and black. Can be multicolored and it has layers(bands) streak= white Crystal system= orthorhombic Crystal forms= Crystals are tabular, prismatic, and as grainy, platy, and coxcomb aggregates. Individual crystals are often twinned, and can be quite large. May also be massive, nodular, fibrous, stalactitic, and as perfect rosettes. Crystals may occasionally contain phantom growths. transparency= transparent to opaque luster= vitreous to pearly cleavage= 1,1 basal- 2,1, prismatic , and 3,1 pinacoid fracture= uneven Tenacity- brittle

Augite

Chemical composition= silicate of calcium, sodium, magnesium, and iron. Occasionally with zinc, manganese, and titanium impurities. color= green, grayish green, greenish brown, dark brown, and black streak= light green to colorless Crystal system= monoclinic or diamond shape Crystal forms= Often as prismatic crystals with a rectangular or octagonal cross section. Also in short, stubbycrystals with a flattened slightly pyramidal termination. Other forms are columnar, grainy, massive, fibrous, and in disordered aggregates of rectangular crystals. May also be in penetration twins with v-shaped saddles. Crystals from certain localities have partially hollow etchings. transparency= opaque. Translucent in thin sections luster= vitreous to dull cleavage= 1,2- prismatic Can exhibit parting in one direction fracture= uneven to splintery tenacity= brittle group= silicates, inosilicates, pyroxene group

Gold

Chemical formula= Au composition= Gold, with small amounts of silver; sometimes also copper and iron color= Golden yellow to brass yellow streak= golden yellow Crystal system= isometric Crystal forms= Octahedral, dodecahedral, and cubic crystals occur, as well as combinations of these forms, but they are uncommon and are often distorted. Dendrites, wires, nuggets, encrustations, and small flakes are the more common forms. Crystals are often stacked into elongated groups, and may form in lines or patterns, especially in herringbone formation. Spinel twinning in groups of small crystals is well-known habit. Crystals may form in hopper growths. transparency= opaque luster = metallic cleavage= none fracture= hackly tenacity= ductile and malleable

Muscovite

Composition: Basic potassium aluminum silicate, sometimes with some chromium or manganese replacing the aluminum Color: Colorless, white, beige, yellow, brown, gray, green, pink, purple, red, black; occasionally multicolored Streak: Colorless Crystal system: Monoclinic Crystal forms and aggregates: Crystals are in thick flakes, micaceous masses and groupings, and in tabular, foliated, flaky, and scalyforms. Crystals may also be elongated with one dimension flat, or stubby triangular or hexagonally shaped crystals. Also forms interesting aggregates of dense bladed crystals, thick rosettes, uniquely twinned star-shaped formations, and rounded botryoidal and globular masses of dense flakes. May also form pseudomorphs after other minerals, assuming the original minerals crystal shape. Transparency: Transparent to translucent Luster: Pearly Cleavage: 1,1 Fracture: Uneven Tenacity: Sectile, Elastic

Fluorite

Composition: Calcium fluoride Color: occurs in all colors, including colorless, white, purple, blue, red, pink, orange, yellow, brown, green, gray, and black. May also be multicolored and banded. Streak: White Crystal system: Isometric Crystal forms and aggregates: Most commonly octahedrals and cubic; seldom in dodecahedral crystals. Crystals may also be a combination of octahedra and cubes, and dodecahedral growths may also be present, forming complex and interesting crystals. Cleavage marks are present on most crystals. Cleavage fragments from large crystals are also prevalent; in octahedra, the cleavage fragments are flat, triangular shaped pieces, and cubic cleavage fragments are flat, three dimensional rectangles. Crystals frequently form penetration twins, where one cube is intergrown in another. Also occurs as clusters of intergrown cubes, grainy, botryoidal, as spherical balls, and massive. Transparency: transparent to translucent Luster: Vitreous Cleavage: 1, all sides Fracture: Conchoidal Tenacity: Brittle

Goethite

Composition: Iron hydroxide, often with some manganese Variable formula: (Fe,Mn)O(OH) Color: Black, brown, yellowish-brown, reddish-brown, yellow. May be iridescent with a multicolored rainbow-like display of darker toned colors. Rarely banded. Streak: Brownish-yellow to yellow Crystal system: Orthorhombic Crystal forms and aggregates: Individual crystals are in small, flattened blades and plates, or finely acicular with a velvety appearance. Most often in botryoidal, reniform, or stalactitic aggregates of radiating crystals or ball-like crystals. Also grainy, in veins, concretionary, oolitic, and in earthy masses. Often assumes the shape of other minerals forming a pseudomorph in place of the original mineral or as a coating above it. Transparency: Opaque Luster: Submetallic, silky, dull Cleavage: 1,1 Fracture: Splintery, uneven Tenacity: Brittle

Magnetite

Composition: Iron oxide. May contain several different elemental impurities partially replacing both the first and the second iron. Color: Dark gray to black Streak: Black Crystal system: Isometric Crystal forms and Aggregates: Crystals are usually octahedral, and they may be very well-formed. Less commonly dodecahedral. Crystals may exhibit interesting combinations of octahedral and dodecahedral faces. Spinel twinning is an occasional habit, and an unusual cubic form is well-known from one specific locality. Crystals may be striated, and some octahedral crystals contain layer growths. Also drusy, grainy, in veins, as large embedded grains, as rounded crystals, and massive. Transparency: Opaque Luster: Metallic Cleavage: None. May exhibit parting. Fracture: Subconchoidal to uneven Tenacity: Brittle

Olivine

Composition: Magnesium iron silicate. The series ranges from the magnesium end member, Forsterite (Magnesium silicate), through the intermediary member, (also known as Chrysolite), to the iron end member, Fayalite (Iron silicate). Color: Forsterite and can be olive-green, light green, dark green, yellow-green, yellow-brown, and brown. Rarely white, gray, or orange. Streak: Colorless Crystal System: Orthorhombic Crystal systems and aggregates: Most often as rounded grains, in dense aggregates of grainy crystals, as fractured masses, and as rounded waterworn pebbles and grains. Large crystals, which are prismatic and stubby, are uncommon except at a few select localities. Crystals often have rounded faces. Transparency: Transparent to translucent Luster: Vitreous Cleavage: 2,1 ; 3,1- forming a 90º angle Fracture: Conchoidal Tenacity: Brittle

Agate/Onyx

Composition: Silicon Dioxide Color: Multicolored in banded formation. Colors include white, blue, red, green, yellow, orange, brown, pink, purple, gray, and black. Some rarer forms of Agate are iridescent. Streak: White Crystal System: Hexagonal Crystal Forms and Aggregates: is a banded microcrystalline form of the mineral Quartz, and does not occur in visible crystals. It occurs in nodules, in massive form, as botryoidal, mammillary, and stalactitic formations, as smooth rounded pebbles, as amygdules, and as the linings of geodes. Transparency: Translucent to opaque Luster: Vitreous Cleavage: None Fracture: Conchoidal

Albite

Silicate. Feldspar- Plagioclase Series composition= sodium aluminum silicate ( sodium might be replaced by potassium or calcium) Color= white, colorless, cream, light blue, light yellow, light green, pale red,,light brown ,and gray streak= white Crystal system= triclinic Crystal forms= Crystals are usually flat and bladed, and often in compact groupings. Also occurs as tall prismatic and short, stubby, tabular crystals. These crystals are usually in groupings, and rarely occur singly on a matrix. Crystal twins are common. Other forms are grainy, massive, columnar, rosette, and coxcomb. Crystals are sometimes striated. Transparency= transparent to translucent Luster= vitreous to pearly cleavage= 2,1 - basal ; 2,1 - prismatic ; 3,1 - pinacoidal. The cleavage angle is about 90º. Fracture= subconchoidal to uneven Tenacity = brittle

Biotite

Silicates. Mica group. Composition: basic fluoro potassium, magnesium, iron aluminium silicate. Color: Black, dark brown, dark green, reddish black. Individual group member minerals such as Phlogopite and Eastonite can be in lighter colors. Streak: White Crystal system: monoclinic- Three axes, all of them are unequal in length. Two of them are at right angles to each other, while the third is lies at an angle other than 90°. Crystal forms and aggregates: Crystals are in thick flakes, micaceous masses and groupings, and in tabular, foliated, flaky, and scaly forms. Crystals may also be elongated with one dimension flat, or stubby triangular or hexagonally shaped crystals. Also forms in prismatic barrel-shaped or tapered pyramid-shaped crystals composed of dense parallel plates, and as rounded nodules of dense crystals. Transparency: Translucent to opaque. Thin flakes will always be translucent if held up to the light. Luster: Pearly Cleavage: 1,1 Fracture: uneven tenacity= sectile and elastic

Orthoclase

Silicates; Feldspar - potassium feldspar Composition: Potassium aluminum silicate Color: White, yellow, colorless, pink, orange, light blue, light green, brown, gray Steak: white Crystal System: Monoclinic Crystal Forms and aggregates: Occurs in well shaped prismatic and tabular crystals, which are sometimes striated. Crystals often form penetration twins and repeated twins, in the form of Carlsbad twins, Baveno twins, and Manebach twins. Also occurs massive, grainy, and as rounded, waterworn stones. Transparency: transparent to opaque Luster: Vitreous to pearly Cleavage: 2,1 - basal ; 2,1 - prismatic ; 3,1 - pinacoidal. The cleavage angle is about 90º. Fracture: conchoidal to uneven Tenacity: brittle

Epidote

Silicates; Sorosilicates Chemical Composition: Basic calcium aluminum iron silicate. Color: Light to dark-green, olive-green, brownish-green, yellowish-green, yellow, brown, black. Transparent forms can be strongly pleochroic with a greenish color on one angle and brownish color on the other angle. Streak: White Crystal System: Monoclinic Crystal forms and aggregates: Usually in long slender prismatic crystals; also in thick tabular crystals. Crystals are sometimes striated and may have interesting wedge-shaped terminations. They also may have etchings or growth layers, and may contain late-growth small crystals layers growing upon a larger crystal. Also columnar reticulated, acicular, radiating, in fan-shaped and wheat sheaf crystal groups, and in long, slender fragile interconnected crystal groupings. May also form as a thin microcrystal crusting and may be massive. Transparency: Transparent to nearly opaque Luster: Vitreous Cleavage: 1,1 Fracture: Uneven Tenacity: Brittle

Citrine

VARIETY OF QUARTZ composition= silicon dioxide Crystal forms= Most often as protruding clusters of pyramids on a geode base. Also occurs as short, stubby, terminated crystals, either singular or in drusy aggregates, and occasionally as long prismatic crystals and groupings. Also occurs massive and crusty. Crystal system= hexagonal color=yellow, yellow-brown, orange, dark orange-brown, reddish-brown transparency= transparent to translucent luster= vitreous cleavage= indiscernible Fracture- conchoidal tenacity= brittle

Rose quartz

Variety of Quartz Composition: Silicon dioxide, usually with impurities of iron oxides or organic substances. Color: pale-pink to rose-red Streak: white Crystal system= hexagonal luster= vitreous transparency= transparent to translucent cleavage= indiscernible Mineral class= quartz

Fossiliferous limestone

Variety of limestone Fossiliferous limestone is any type of limestone, made mostly of calcium carbonate (CaCO3) in the form of the minerals calcite or aragonite, that contains an abundance of fossils or fossil traces. The fossils in these rocks may be of macroscopic or microscopic size. The sort of macroscopic fossils often include crinoid stems, brachiopods, gastropods, and other hard shelled mollusk remains.

Oolitic limestone

Variety of limestone Oolitic limestone is a carbonate rock made up mostly of oolites (or ooids) which are sand-sized carbonate particles that have concentric rings of CaCO3. These rings are formed around grains of sand or shell fragments that were rolled around on the shallow sea floor, gathering layer after layer of limestone.

Chalcedony

Variety of quartz composition= silicon dioxide color= White, blue, red, green, yellow, orange, brown, pink, purple, gray, black, colorless, and multicolored. Often banned in many different color combinations, and a few rarer forms are iridescent. streak= white Crystal system= hexagonal Crystal forms: being a microcrystalline variety of the mineral Quartz, does not occur in visible crystals. It occurs in botryoidal, mammillary, stalactitic, massive, nodular forms, as smooth rounded pebbles, as banded masses, as amygdules, and as the linings of geodes. transparency= transparent to opaque fracture= conchoidal tenacity= brittle luster= vitreous, waxy, or dull cleavage= none

Chert

a hard, dark, opaque rock composed of silica (chalcedony) with an amorphous or microscopically fine-grained texture. It occurs as nodules (flint) or, less often, in massive beds. composition= Chert is a microcrystalline or cryptocrystalline sedimentary rock material composed of silicon dioxide (SiO2). It occurs as nodules, concretionary masses, and as layered deposits. Chert breaks with a conchoidal fracture, often producing very sharp edges. Early people took advantage of how chert breaks and used it to fashion cutting tools and weapons. The name "flint" is also used for this material. Chert is a microcrystalline silicon dioxide (SiO2). As chert nodules or concretions grow within a sediment mass, their growth can incorporate significant amounts of the surrounding sediment as inclusions. These inclusions can impart a distinctive color to the chert. Environments of formation= Chert can form when microcrystals of silicon dioxide grow within soft sediments that will become limestone or chalk. In these sediments, enormous numbers of silicon dioxide microcrystals grow into irregularly-shaped nodules or concretions when dissolved silica is transported to the formation site by the movement of groundwater. If the nodules or concretions are numerous, they can enlarge and merge with one another to form a nearly continuous layer of chert within the sediment mass. Chert formed in this manner is a chemical sedimentary rock. Some of the silicon dioxide in chert is thought to have a biological origin. In some oceans and shallow seas, large numbers of diatoms and radiolarians live in the water. These organisms have a glassy silica skeleton. Some sponges also produce "spicules" that are composed of silica. When these organisms die, their silica skeletons fall to the bottom, dissolve, recrystallize, and might become part of a chert nodule or chert layer. Chert formed in this way could be considered a biological sedimentary rock. texture= Chert is a microcrystalline or cryptocrystalline sedimentary rock material composed of silicon dioxide (SiO2). ... Flint is a hard, tough, chemical or biochemical sedimentary rock that breaks with a conchoidal fracture. It is a form of microcrystalline quartz that is typically called "chert" by geologists.

Amazonite/ Microcline

color= blue, green, purple, gray, multicolored. often has white lines or alternating streaks mixed in, and can have uneven color distribution. A deep forest-green color is most preferred, but gemstones can also be light green and bluish-green. Grayish-green and very faint green stones also exist, but are not commonly used as gemstones. transparency= transparent to opaque Crystal system= triclinic luster=vitreous Mineral class/ classification= microcline and feldspar, silicates tectosilicates luster= vitreous composition= potassium aluminum silicate cleavage= 2,1 - basal ; 2,1 - prismatic ; 3,1 - pinacoidal. The cleavage angle is about 90º. tenacity= brittle fracture= conchoidal to uneven

Topaz

composition= Aluminum fluoro-hydroxyl-silicate color= colorless, white, yellow, orange, brown, pink, light purple, gray, light blue, greenish blue, green. Occasionally multicolored. streak= colorless Crystal system= orthorhombic Crystal form= Prismatic, tabular, and stubby crystals, usually striated and sometimes quite large. Crystals may contain numerous faces, and often have complex terminations. Also occurs columnar, massive, grainy,radiating, and as rounded, waterworn pebbles. May also be in the form of feldspar as a pseudomorph. transparency= transparent to opaque luster= vitreous cleavage= 1,3 basal fracture= subconchoidal tenacity= brittle groups= Silicates; Nesosilicates

Staurolite

composition= Basic aluminum iron silicate, often with magnesium and sometimes with zinc and lithium. color= Brown, grayish brown, gray, yellowish-brown, reddish brown streak= white Crystal system= monoclinic Crystal form= In pseudo-orthorhombic crystals, usually in rectangular form with a hexagonally-shaped cross section. Crystals often have a triangular formation on the termination. Crystals are usually prismatic, but may also be short and stubby, as well as tabular. Most often in penetration twins, in the form of perfect perpendicular crosses, 60° penetration twins, and occasionally even in triple-twinned, star-shaped combinations. Also in groupings of several crystals, and in twins where a smaller twinned crystals appears to be swallowed by a larger one. transparency= Translucent to opaque. Rarely transparent. luster= vitreous and dull tenacity= brittle fracture=uneven to subconchoidal cleavage= 3,1

Talc

composition= Basic magnesium silicate color= White, beige, gray, yellow, brown, pink, purple, blue, green. Rarely colorless. streak= white Crystal system= monoclinic Crystal forms= Most often as large distorted masses and foliated sheets and plates. Also micaceous, radiating, botryoidal, and in fibrous masses. Crystallized examples, which include flat tabular crystals, are rare and are almost always microscopic. Very commonly pseudomorphs after many minerals, assuming their original shape. Some minerals commonly pseudomorphs are Quartz, Calcite, Dolomite, and Pyroxenes. transparency= Transparent to opaque luster= pearly and waxy and greasy cleavage= 1,1 fracture= uneven tenacity= sectile

Tremolite

composition= Basic magnesium, calcium, iron silicate color= White, light to dark gray, black, light yellow, light to dark green, emerald green, pink to purple. Rarely colorless. streak= colorless Crystal system= monoclinic Crystal form= As elongated prismatic crystals, in bladed groups, columnar, fibrous, reticulated and acicular. Also occurs radiating, as wheat sheaf formations, as thin hairlike masses, and as tough interlocking fibers which may appear massive. transparency= Transparent to translucent luster= vitreous, silky cleavage= 2,2 prismatic fracture= Uneven, splintery tenacity= Brittle. Fibrous forms are elastic.

Dolomite

composition= Calcium magnesium carbonate. The amount of calcium and magnesium in most specimens is equal, but occasionally one element may have a slightly greater presence than the other. Small amounts of iron and manganese are sometimes also present. color= Colorless, white, gray, peach, pink, yellow, and orange. Rarely yellow, green, red, and black. streak= white Crystal system= hexagonal Crystal forms= most commonly forms in groups of small rhombohedral crystals very often with curved, saddle-like faces. Also occurs prismatic, (although usually slightly curved), grainy, botryoidal, coxcomb, and massive. A rare form from a few locations is as colorless transparent rhombohedrons or rhombohedral aggregates. transparent= transparent to translucent on thin splinters luster= vitreous to pearly cleavage= 1,3 - rhombohedral fracture= conchoidal tenacity= brittle

Hornblende

composition= Complex basic silicate of sodium, calcium, magnesium, and aluminum. Some members have potassium, titanium, and fluoride. color= black, dark green, dark brown, dark gray. steak= colorless Crystal system= monoclinic Crystal form= As prismatic or tabular crystals with a diamond-shaped cross-section. Rarely in individual crystals; almost always in dense groups of platy or grainy crystals. Also columnar, radiating, acicular, fibrous, in veins, and massive. transparency= Opaque. May be slightly translucent on thin cross-sections under strong back-lighting. luster= Vitreous, sub metallic, dull cleavage= 2,2 - prismatic fracture- = uneven and splintery tenacity= brittle

Opal

composition= Hydrous silicon dioxide. The water can range from 3% to 21% of the total weight, but is usually between 6% to 10%. color= Colorless, white, yellow, orange, red, purple, blue, green, gray, brown, and black. These are some of the base colors. Certain ones display different colors when viewed from different directions, or when the stone is turned, or when the light source is moved. This phenomenon, called play of color, gives a stone color flashes, or schillers of different colors which vary from stone to stone. Also occurs multicolored and banded. streak= white Crystal system= Amorphous Crystal form= is amorphous and does not occur in any crystals, except when it forms as a pseudomorph after another mineral. Habits include massive, botryoidal, reniform, stalactitic, earthy, nodular, as veins, in crusts, and in accumulating mounds. It often pseudomorphs after organic matter such as wood, shell, and bone. transparency= Transparent to opaque luster= Usually vitreous, but may also be pearly, waxy, or resinous. cleavage= none fracture= conchoidal tenacity= brittle

Tourmaline

composition= In some less common varieties, the Al may be replaced by other elements. For example, in Uvite, the Al is partially replaced by Mg. color= is extremely varied in color. Colors include black, brown, green, red, pink, blue, and gray. White, colorless, yellow, orange, and purple colors are less common. Crystals are frequently multicolored, containing two or more distinct colors. Some specimens are pleochroic. streak= white Crystal system= hexagonal Crystal form= Usually as elongated prismatic crystals that are heavily striated. Also as short, stubby, prismatic crystals. Most crystals have a rounded, triangular cross-section. Seldom in tabular crystals. Aggregates include columnar, radiating, botryoidal, stalactitic, in dense groups of tiny, elongated needles, and in compact masses. transparency= transparent to opaque luster= Vitreous. Some black and brown specimens may be dull. cleavage= 3,2 fracture= conchoidal to uneven tenacity= brittle

Pyrite

composition= Iron sulfide, sometimes containing small amounts of cobalt, nickel, silver, and gold color= Yellowish gray to gray. Some specimens oxidize and form a yellow-brown or iridescent film on exposed crystal faces. streak= Black with a slightly green tinge Crystal system= isometric Crystal form= Can form in extremely well-crystallized examples of cubes, and octahedrons. Combinations of these forms also occur. An icosahedron formed from a combination of an octahedron and pyritohedron is also known. Crystals frequently form penetration twinning, especially in the cubic form. Cubes are sometimes elongated in rectangular form. Also occurs massive, radiating, grainy, flaky, drusy, mammillary, encrusting, nodular, tuberose, fibrous, in concretions, and as groups of small crystals. Crystals are frequently striated. transparency= opaque luster= metallic cleavage= none fracture= conchoidal tenacity= brittle

Rhodonite

composition= Manganese silicate, sometimes with some calcium, iron, and magnesium color= Red, pink, orange-red, and brownish-red. Massive specimens often have black veins running through them. Some specimens tarnish black or brown upon exposure to air. streak= colorless Crystal system= triclinic Crystal forms= Forms in tabular and rectangular prismatic crystals. They are sometimes rounded on the edges and in columnar aggregates. Most often in grainy masses, in compact groupings, coxcomb aggregates, fibrous groupings, and massive. transparency= Transparent to translucent luster= vitreous cleavage= 2,2 - forming at an angle near 90º fracture= hackly and uneven tenacity= brittle group= Silicates; Inosilicates

Amethyst

composition= Silicon dioxide. Its purple coloring is usually caused by impurities of iron or manganese compounds. color= Light to dark purple. Sometimes banded with purple and whitish lines. May also be mixed together with Citrine. streak= white Crystal system= hexagonal Crystal form= Most often as protruding clusters of pyramids on a matrix base. These "pyramids" can be quite large. Also occurs as tall prismatic crystals, as short stubby crystals, in drusy aggregates, massive, in geodes, and as rounded waterworn stones. A very interesting habit is as crystalline crusts inside volcanic pipes. Crystals are usually striated horizontally, and occasionally have a scepter growth. transparency= Transparent to translucent tenacity= brittle fracture= conchoidal cleavage= indiscernible luster= vitreous

Silver

composition= Silver, sometimes mixed with gold, mercury, arsenic, and antimony color= Silver-white on untarnished surfaces. Tarnishes dark yellow to black. streak= Silver-white to light gray. Streak shiny. Crystal system= isometric Crystal form= Cubic, octahedral, and dodecahedral crystals occur, but are very rare. Usually occurs dendritic, wiry, massive, as grains and scales, and as groups of tiny crystals. transparency= opaque luster= metallic cleavage= none fracture= hackly tenacity= malleable and ductile

Sodalite

composition= Sodium aluminum silicate with chlorine, and occasionally sulfur. color= Most often blue, less commonly purple, pink, gray, green, brown, white, and colorless. May also be multicolored blue with white and gray veins. streak= white Crystal system= Crystals, which are dodecahedral, are rare and will usually have complex or rounded terminations. Most often massive, grainy, and nodular. Crystal form= Crystals, which are dodecahedral, are rare and will usually have complex or rounded terminations. Most often massive, grainy, and nodular. transparency= transparent to opaque luster= vitreous to glassy. May also be dull cleavage= 3,6 fracture= uneven tenacity= brittle

Sphalerite

composition= Zinc sulfide, usually with some iron, sometimes with magnesium, manganese. In a few rare localities, it contains cadmium, indium, and gallium. color= Black, brown, red, orange, yellow, green, gray. Rarely colorless. Some specimens contain crystals of different colors, and there is also a brown, globular, banded variety. streak= Pure has a white streak. However, impurities are almost always present, giving this mineral a light brown streak. The streak will always be a lighter color than the specimen. Crystal system= isometric Crystal form= Most commonly as tetrahedral crystals, which are usually twinned and grouped together. They may closely resemble octahedral crystals. Also occurs as groupings of distorted dodecahedral and cubic crystals. Crystal faces are usually rounded or curved. May also be massive, grainy, botryoidal, stalactitic, and as large, distorted cleavage fragments. transparency= transparent to opaque luster= Metallic, sub-metallic, adamantine, resinous cleavage= 1,all sides, forming a dodecahedron fracture= conchoidal tenacity= brittle

Corundum

composition= aluminum oxide color= Many colors, including blue, red, violet, pink, green, yellow, orange, gray, white, colorless, and black. Occasionally also multicolored or striped. Streak= white Crystal system= hexagonal Crystal form= Crystals occur as hexagonally shaped prismatic and tabular crystals, and as bipyramidal hexagons that are wider in the center and taper thinly on the ends. Crystals are usually elongated and striated,crosswise, and sometimes occur in thin plates. Crystals are commonly smooth or rounded on the edges due to alluvial action. Also as barrel-shaped hexagonal crystals, modified octahedrons, massive, and as rounded, waterworn alluvial pebbles. Crystals are sometimes striated or etched. transparency= transparent to opaque luster= vitreous to adamantine cleavage= None, but commonly exhibits rhombohedral and basal parting fracture= uneven tenacity= brittle

Bauxite

composition= basic aluminium hydroxide color= beige, white, yellow, gray, brown, reddish-brown, pink Streak= white Crystal form= amorphous(undefined) Crystal forms= massive with clay-like masses transparency= opaque Luster= dull cleavage= none fracture= earthy tenacity= brittle group=oxides and hydroxides

Azurite

composition= basic copper carbonate color= blue to a very dark blue streak= light blue Crystal system= monoclinic Crystal forms= Usually in small crystals, which are in prismatic, tabular, or equidimensional form. Crystals are sometime striated. Other forms are massive, crusty, radiating, fibrous, earthy, columnar, stalactitic, as thin needles, and in ball-like aggregates. Also occurs in dense groups of tabular or prismatic crystals. May also form as a pseudomorph over other minerals, retaining the original crystal shape of the mineral that it formed a pseudomorph over. transparent= opaque. Rarely translucent luster= vitreous to dull cleavage= 2,1 and 3,2 fracture= conchoidal or splintery tenacity= brittle

Beryl

composition= beryllium aluminium silicate. Occasionally with some sodium, lithium, and cesium color= Light to emerald green, light to deep sky-blue, blue-green, yellow, pink, purple, red, orange, brown, colorless, white, and gray. May also be multicolored blue, green, yellow, or white, and may also have deeper color highlights on one crystal end. streak= colorless Crystal system= hexagonal Crystal form= often crystallizes in perfect, six-sided hexagons. Crystals are usually as individual prismatic hexagons. Crystals may be enormous in size; some 30 foot long (8 meter), well-crystallized examples have been found. May also be short, stubby crystals, and occasionally in tabular crystals and plates. The bases of crystals are usually flat; pyramidal terminations are rare. Also occurs in columnar aggregates, in distorted etched crystals, and massive. Occasionally in drusy or platy aggregates and as bundles of thin, long crystals. Crystals may be striated lengthwise. transparency= transparent to opaque luster= vitreous to waxy cleavage= 3,1= basal fracture= uneven to conchoidal tenacity= brittle

Aragonite

composition= calcium carbonate sometimes with strontium or lead and zinc. streak= white color= white, colorless , brown, gray, yellow, red, pink, purple, orange, blue, green Crystal system= orthorhombic Crystal forms=The most common crystallized form is in pseudohexagonal trillings, which can be in the form of long, slender, prismatic crystals or short stubby ones. Rarely occurs as single, untwinned crystals. Many aggregates exist, such as acicular, radiating, fibrous, columnar, stalactitic, botryoidal, pisolitic, oolitic, tuberose, granular, encrusting, and ball-like protrusions of pseudohexagonal crystals. transparency= transparent to opaque luster= vitreous to dull cleavage= 3,1 prismatic and indiscernible - 2 fracture= subconchoidal tenacity= brittle

Graphite

composition= carbon color= silver-gray to black streak= black Crystal system= hexagonal Crystal forms= Crystals consist of thin hexagonal plates or distorted clusters of flaky plates on a matrix. Large thick hexagonal crystals are rare. Most often occurs as veins, as foliated masses, and in massive form. Small, rounded ball-like aggregates and radiating spheres also occur, as do rounded, waterworn pebbles. transparency= opaque luster= metallic cleavage= 1,1, basal fracture= conchoidal tenacity= brittle. Thin flakes are flexible

Chalcopyrite

composition= copper iron sulfide color= Brass yellow to golden yellow; sometimes dark brown to black. Tarnishes to a multicolored purple, blue, and red. steak= black with a slight green tinge Crystal system= tetragonal/ Any mineral that falls under the following specifications belongs to the tetragonal crystal system: Three axes, two are equal in length, one is unequal. All three axes are at 90° to each other. Crystal forms= Crystals resemble tetrahedrons and octahedrons (eight sided polyhedron), but they are slightly asymmetrical and therefore are categorized in the tetragonal system. Also occurs massive, grainy, reniform, and as groups of small, distorted crystals. Crystals are commonly striated in different directions on different crystal faces. transparency= opaque luster= metallic cleavage= indiscernible fracture= uneven tenacity= brittle

Bornite

composition= copper iron sulfide color= Copper-red to yellowish brown on fresh surfaces. Quickly tarnishes to a multicolored purple, blue, and red. streak= dark gray to black Crystal system= orthorhombic Crystal form= forms as isometric crystals at high temperatures, but when it cools down to normal temperatures it crystallizes in the orthorhombic system. However, the crystals retain their original isometric crystals. Crystals are rare, and are in cubic or dodecahedral form. Octahedral shaped crystals are extremely rare. Occurs mostly massive, as well as in groups of tiny crystals and globular. Transparency- opaque luster= metallic cleavage= indiscernible tenacity= brittle fracture= conchoidal

Hematite

composition= iron oxide. Can contain small amounts of titanium color= Black, gray to silver gray, brown to reddish brown, red. Some specimens are iridescent, and other are multicolored or banded gray and dark red. streak= red to reddish brown Crystal system= hexagonal Crystal forms= Crystals occurs in thin plates, as well as bundles of small micaceous plates, and in thin splinters. Most commonly massive, mammillary, botryoidal, reniform, oolitic, stalactitic, and radiating. Scalenohedral and rhombohedral crystals occur, as well as tabular and groups of tabular crystals. Crystals are often striated. Dendritic and rosette forms are also found. May form as a pseudomorph after other minerals, especially as octahedral crystals of Magnetite. transparency= opaque luster= metallic to dull fracture= uneven tenacity= brittle

Milky Quartz

composition= silicon dioxide streak= white Crystal system= hexagonal color= Colorless, white, but cloudy Crystal form= Crystals, which are hexagonal in shape, vary in shape and size. Crystals frequently twin; a famous twinning habit is the Japanese twin, where two crystals contact at a 90º angle. Quartz crystals may also contain a scepter growth, where the top of a crystal bulges out from the rest of the crystal, and may also form as phantom growth, where one crystal forms over another, leaving a ghosted form inside. The crystal structure of Quartz is a very complicated. As a result of a changeover from alpha to beta Quartz, crystals form as hexagonal prisms with modified crystal faces. transparency= transparent to opaque Luster- Vitreous. cleavage= Indiscernible. Seldom exhibits parting. fracture= conchoidal tenacity= brittle

Celestite

composition= strontium sulfate. Sometimes with small amounts of barium color= Blue, white, colorless, orange, orange-brown, light brown, yellow, greenish-blue, gray. Crystals may also be slightly multicolored, with light blue on one end and colorless on the other. streak= white Crystal system= orthorhombic Crystal form= Occurs as prismatic and tabular crystals, and as thin tabular plates. May also occur as thick, pseudohexagonal trillings, as well as dense aggregates of such crystals. Also occurs massive, radiating, grainy, nodular, and botryoidal. May also be as fibrous masses, as dense clusters of tabular crystals, as fragile, elongated crystal clusters, as fillings in geodes, and as cleavage fragments. Crystals are sometimes striated, and occasionally contain phantom growths. transparent= transparent to translucent luster= vitreous to pearly on cleavage edges cleavage= 1,1 - basal ; 2,1 - prismatic ; 3,1 - pinacoidal fracture= uneven tenacity= brittle

Sulfur

composition= sulfur color= bright yellow to yellow brown streak = white Crystal system= orthorhombic Crystal form= Steep dipyramidal and tabular crystals are common. May also be bipyramidal with angled centers. Crystals frequently have hollow skeletons or hoppered growths. Curved and rounded distorted crystals are also common. Small grains, wheat sheaves, and encrustations occur. Massive, earthy specimens are prevalent, and may have bubbly holes throughout. Also occurs as rounded, waterworn masses. transparency= transparent to opaque luster= Adamantine on clean, clear crystal surfaces; otherwise resinous or dull cleavage= 3,2 fracture= conchoidal tenacity= brittle

Galena

composition=Lead sulfide. May contain impurities, such as silver, arsenic, antimony, and copper. Streak and color= steel gray Crystal system= isometric Crystal forms= Crystals, which may be cubes, octahedrons, or a combination of the two frequently occur. Cubes are often partially cleaved. Dodecahedrons are far less common. Also occurs massive, grainy, fibrous, platy, as veins, and as cleavage fragments. transparency= opaque luster=Metallic. Turns somewhat dull after exposure to air. cleavage= 1,3 - Cubic. May exhibit parting on octahedrons. fracture= subconchoidal tenacity= brittle

Copper

composition=copper, commonly associated with iron or silver. color= -red to brown. Tarnishes green, sometimes also blue, brown, red, or black. streak= shiny -red Crystal system= cubic/ isometric Crystal forms= Often found as distorted masses or extremely distorted crystals. Crystals, which are uncommon, are usually cubic or dodecahedral with modified faces. Octahedral crystals do occur, but are very rare. Also occurs as flattened crystals, scales, dendrites, and wires. transparency= opaque luster= metallic cleavage= none fracture= hackly, Type of fracture resembling broken metal, exhibiting sharp, jagged surfaces. This fracture is also known as "jagged" fracture. tenacity= ductile and malleable

Breccia

rock consisting of angular fragments cemented together. Environments of formation= Breccia forms where broken, angular fragments of rock or mineral debris accumulate. One possible location for breccia formation is at the base of an outcrop where mechanical weathering debris accumulates. Another would be in stream deposits near the outcrop such as an alluvial fan. Some breccias form as debris flow deposits. The angular particle shape reveals that they have not been transported very far (transport wears the sharp points and edges of angular particles into rounded shapes). After deposition, the fragments are bound together by a mineral cement or by a matrix of smaller particles that fills the spaces between the fragments. composition= Breccia has many compositions. Its composition is mainly determined by the rock and mineral material that the angular fragments were produced from. The climate of the source area can also influence composition. Most breccias are a mix of rock fragments and mineral grains. The type of rock that the fragments were produced from is often used as an adjective when referring to the rock. Some examples: sandstone breccia, limestone breccia, granite breccia, chert breccia, basalt breccia, and others. Often a breccia will contain many types of angular rock fragments. These are known as polymict breccias or polymictic breccias. Collapse Breccia: Broken rock that originates from a cavern or magma chamber collapse. Fault Breccia: Broken rock found in the contact area between two fault blocks and produced by movement of the fault. Flow Breccia: A lava texture produced when the crust of a lava flow is broken and jumbled during movement. Igneous Breccia: A term used for a rock composed of angular fragments of igneous rocks. "Flow breccia" and "pyroclastic breccia" could be called "igneous breccia." Impact Breccia: A deposit of angular rock debris produced by the impact of an asteroid or other cosmic body. See an article about "impactites." Pyroclastic Breccia: A term used for a deposit of igneous rock debris that was ejected by a volcanic blast or pyroclastic flow. texture= Flow Breccia: A lava texture produced when the crust of a lava flow is broken and jumbled during movement. Igneous Breccia: A term used for a rock composed of angular fragments of igneous rocks. "Flow breccia" and "pyroclastic breccia" could be called "igneous breccia."

Apatite

streak = white color= red, gray, colorless, white ,yellow, brown, pink, purple, blue, green. Rarely multicolored Crystal system= hexagonal Crystal forms= generally forms as well-shaped hexagonal crystals, which may be prismatic, dipyramidal, and stubby. Also as flat, tabular plates, columnar, in stacked parallel growths, as globular masses, acicular, grainy, stalactitic, botryoidal, and earthy. Also in enormous beds of massive material, from which industrial phosphorus is mined. transparency= transparent to translucent luster= vitreous cleavage= indiscernible fracture= conchoidal tenacity= brittle