Science Olympiad Rocks and Minerals (No pics)

Obsidian

*** is an extrusive rock: lava that cooled without forming crystals, giving it a glassy texture

Graphite

Its molecular structure makes *** an excellent dry lubricant wherever temperatures do not get too high. Pencils make use of graphite for the same reason, as *** rubs off on paper so easily. *** is very soft, measuring 1 or 1.5 on the Mohs scale of mineral hardness. *** forms during the metamorphism, under intense heat and pressure, of coal or limestones with a great deal of organic matter in them. Like diamonds, the other crystalline form of carbon, *** can be manufactured artificially, but the natural material is still cheaper. *** is widely used in the metal industry for making crucibles that can resist the heat of the foundry. The earliest nuclear reactors had walls of ***. Nevertheless, under the right conditions, *** burns. The thick graphite walls of the Chernobyl nuclear reactor caught fire during the catastrophic meltdown of 1986.

Silver

Native ***, the element Ag, is quite rare, as ***tends to oxidize readily. *** is usually found in sulfide minerals.

Olivine

Olivine occurs in a range of compositions between pure magnesium silicate (forsterite) and pure iron silicate (fayalite), and olivine composition is often given as a number from zero to 100, where 100 is pure fayalite. Forsterite is white and fayalite is dark brown, but olivine is usually green, like these specimens found in the black basalt pebble beach of Lanzarote in the Canary Islands. Olivine has a minor use as an abrasive in sandblasting. As a gemstone, olivine is called peridot. Olivine prefers to live deep in the upper mantle, where it makes up about 60 percent of the rock. It does not occur in the same rock with quartz (except in the rare fayalite granite). It is unhappy at the Earth's surface and breaks down fairly rapidly (geologically speaking) under surface weathering. This olivine grain was swept to the surface in a volcanic eruption. In olivine-bearing rocks of the deep oceanic crust, olivine readily takes up water and metamorphoses into serpentine.

Diorite

Unlike granite, *** has no or very little quartz or alkali feldspar. Unlike gabbro, *** contains sodic, not calcic plagioclase. Typically, sodic plagioclase is the bright white variety albite, giving *** a high-relief look. If a dioritic rock is erupted from a volcano (that is, if it is extrusive), it cools into andesite lava. In the field, geologists may call a black-and-white rock ***, but true *** is not very common. With a little quartz, *** becomes quartz ***, and with more quartz it becomestonalite. With more alkali feldspar, *** becomes monzonite. With more of both minerals, *** becomes grano***. Maybe this will be clearer on the classification triangle.

Gabbro

Unlike granite, *** is low in silica and has no quartz; also *** has no alkali feldspar, only plagioclase that has a high calcium content. The other dark minerals may include amphibole, pyroxene and sometimes biotite, olivine, magnetite, ilmenite and apatite.*** is named after a town in Tuscany, Italy. You can get away with calling almost any dark, coarse-grained igneous rock ***, but true *** is a narrowly defined subset of dark plutonic rocks.*** makes up most of the deep part of the oceanic crust, where melts of basaltic composition cool very slowly to create large mineral grains. That makes *** a key sign of an ophiolite, a large body of oceanic crust that ends up on land. *** is also found with other plutonic rocks in batholiths when bodies of rising magma are low in silica.igneous petrologists are careful about their terminology for *** and similar rocks, in which "***id," "***ic" and "***" have distinct meanings.

Quartz [Crystal]

same as othes

Gypsum [Satin-Spar]

A fibrous variety of Gypsum or Calcite and Aragonite. The name originally referred to a variety of Calcite found in "Cumberland, England", but the name was eventually used to cover varieties of Aragonite and Gypsum too, so this name is best used as an adjective in conjunction with a mineral name rather than as a specific variety name of its own - see Satin Spar Gypsum and Satin Spar Calcite.

Scoria

Another name for *** is volcanic cinders, and the landscaping product commonly called "lava rock" is ***, as is the cinder mix widely used on running tracks.*** is more often a product of basaltic, low-silica lavas than of felsic, high-silica lavas. This is because basalt is usually more fluid than felsite, allowing bubbles to grow larger before the rock freezes. *** often forms as a frothy crust on lava flows that crumbles off as the flow moves. It also is blown out of the crater during eruptions. Unlike pumice, *** usually has broken, connected bubbles and does not float in water.

Pyrite

*** can occur in relatively large grains associated with quartz and milky-blue feldspar. *** has a Mohs hardness of 6, a brass-yellow color and a greenish black streak. *** resembles gold slightly, but gold is much heavier and much softer, and it never shows the broken faces that you see in these grains. Only a fool would mistake it for gold, which is why *** is also known as fool's gold. Still, it's pretty, it's an important geochemical indicator, and in some places *** really does include silver and gold as a contaminant.

Magnetite

*** is the only mineral that exhibits strong magnetism, although others like ilmenite, chromite and hematite may have weakly magnetic behavior. *** has a Mohs hardness of about 6 and a black streak. Most *** occurs in very small grains. A chunk of well-crystallized *** like the round specimen is called a lodestone. *** also occurs in well-formed octahedral crystals. *** is a widespread accessory mineral in iron-rich (mafic) igneous rocks, especially peridotite and pyroxenite. It also occurs in high-temperature vein deposits and some metamorphic rocks.

Celestite

*** (or ***) is strontium sulfate, SrSO4, found in scattered occurrences with gypsum or rock salt. Its pale blue color is distinctive.

Ulexite

***is an evaporite mineral that forms in alkali salt flats where the local water is rich in boron. It has a hardness of about 2 on the Mohs scale. In rock shops, cut slabs of *** like this one are commonly sold as "TV rock." It consists of thin crystals that act like optical fibers, so if you lay it on a paper, the printing appears projected on the upper surface. But if you look at the sides, the rock is not transparent at all. On the surface,*** takes the shape of soft-looking masses and is often called "cotton ball." It also occurs beneath the surface in veins similar to chrysotile, in which the crystal fibers run across the thickness of the vein.

Quartz [Citrine]

Citrine is the yellow to brownish-red variety of the mineral Quartz. It is a widely used as a gemstone, and after Amethyst it is the most popular Quartz gem. Most Citrine is formed by heat treating purple Amethyst. Citrine may also be produced by heat-treating Smoky Quartz from certain localities. In some Amethyst deposits, the Amethyst has been partially or fully changed over to yellow Citrine by natural means of heating. Natural Citrine, which is rare, is yellow to orange-yellow, and occurs in much lighter hues than the heat-treated material, which is dark orange-brown to reddish-brown. Virtually all heat-treated material has a reddish tint, whereas the natural specimens do not. Natural light yellow Citrine is often called "Lemon Quartz" on the gemstone market. Sometimes Citrine has a "smoky" hue to it, and can be borderlined between Citrine and Smoky Quartz, with either definition being correct.

Shale

Geologists are strict with their rules on sedimentary rocks. Sediment is divided by particle size into gravel, sand, silt and clay. Claystone must have at least twice as much clay as silt and no more than 10 percent sand. It can have more sand, up to 50 percent, but that is called a sandy claystone. (See all this in the Sand/Silt/Clay ternary diagram.) What makes a claystone *** is the presence of fissility—it splits in more or less thin layers whereas claystone is massive. *** can be fairly hard if it has a silica cement, making it closer to chert, but usually it is soft and easily weathers back into clay. *** may be hard to find except in roadcuts, unless a harder stone on top of it protects it from erosion. When *** undergoes greater heat and pressure, it becomes the metamorphic rock slate. With still more metamorphism, it becomes phyllite, then schist.

Gypsum [Selenite]

Gypsum occurs in nature as flattened and often twinned crystals, and transparent, cleavable masses called selenite. Selenite contains no significant selenium; rather, both substances were named for the ancient Greek word for the Moon. Selenite may also occur in a silky, fibrous form, in which case it is commonly called "satin spar". Finally, it may also be granular or quite compact. In hand-sized samples, it can be anywhere from transparent to opaque. A very fine-grained white or lightly tinted variety of gypsum, called alabaster, is prized for ornamental work of various sorts. In arid areas, gypsum can occur in a flower-like form, typically opaque, with embedded sand grains called desert rose. It also forms some of the largest crystals found in nature, up to 12 metres (39 ft) long, in the form of selenite.[8]

Feldspar [Orthoclase Group]

Orthoclase (endmember formula KAlSi3O8) is an important tectosilicate mineral which forms igneous rock. The name is from the Greek for "straight fracture," because its two cleavage planes are at right angles to each other. Alternate names are alkali feldspar, potassium feldspar and K-feldspar. The gem known as moonstone (see below) is largely composed of orthoclase.

Limestone Crystalline

Rock Type- Sedimentary Colors-- white, usually light colored-- impurities Minerals Found in it-calcite Mineral Size-fine to coarse, crystal texture Commercial Use-building materials, lime, soil fertilizer Special Features-fizzes to HCl, crystalline texture Clastic or Non-Clastic- Clastic or chemical precipitation

Copper

This wiry aggregate formed as metal-bearing fluids worked their way into channels and pore spaces in a preexisting matrix, probably near a volcanic zone. There are many different scenarios that mobilize and redeposit *** in the upper crust. Because native *** corrodes fairly quickly at surface conditions, specimens like this don't last long (unlike gold). *** nuggets are well known in places like Minnesota or Michigan's Upper Peninsula, which was a *** district for many years. There *** metal appears in extremely old rocks of the Canadian Shield. Native *** has a distinctive ***-colored streak.

Quartz [Milky]

white, opaque version of quartz

Apatite

*** ...a family of minerals centered around fluor***, or calcium phosphate with a bit of fluorine, with the formula Ca5(PO4)3F. General formula for the *** group is thus (Ca,Sr,Pb)5[(P,As,V,Si)O4]3(F,Cl,OH). Because fluor*** makes up the framework of teeth and bones, we have a dietary need for fluorine, phosphorus and calcium. *** is usually green to blue, but its colors and crystal forms vary, and *** can be mistaken for beryl, tourmaline and other minerals. It is most noticeable in pegmatites, where large crystals of even rare minerals are found. The main test of *** is by its hardness, which is 5 in the Mohs scale. **** can cut as gemstone but soft.*** also makes up sedimentary beds of phosphate rock. There it is a white or brownish earthy mass, and the mineral must be detected by chemical tests.

Anthracite Coal

*** *** is a hard, compact variety of mineral *** that has a high luster. It has the highest carbon content, the fewest impurities, and the highest calorific content of all types of ***, which also include bituminous *** and lignite.*** is the most metamorphosed type of *** (but still represents low-grade metamorphism), in which the carbon content is between 92.1% and 98%.The term is applied to those varieties of *** which do not give off tarry or other hydrocarbon vapours when heated below their point of ignition. *** ignites with difficulty and burns with a short, blue, and smokeless flame.*** is categorized into standard grade, which is used mainly in power generation, and high grade (HG) and ultra high grade (UHG), the principal uses of which are in the metallurgy sector. *** accounts for about 1% of global *** reserves,[4] and is mined in only a few countries around the world.

Limestone Fossiliferous

*** may refer to the following limestones containing fossils:

Halite

*** is sodium chloride, NaCl, the same mineral you use as table salt. It is the most common halide mineral.

Augite

*** is the most common pyroxene, with the formula (Ca,Na)(Mg,Fe,Al,Ti)(Si,Al)2O6. *** is usually black, with stubby crystals. It is a common primary mineral in basalt, gabbro and peridotite and a high-temperature metamorphic mineral in gneiss and schist.

Breccia

*** ("BRET-cha") is usually listed under sedimentary rocks, but igneous and metamorphic rocks may become shattered, too. It is safest to think of ***tion as a process rather than *** as a rock type. As a sedimentary rock, *** is a variety of conglomerate.There are many different ways to make ***, and usually geologists add a word to signify the kind of *** they're talking about. A sedimentary *** arises from things like talus or landslide debris. A volcanic or igneous *** forms during eruptive activities. A collapse *** forms when rocks are partly dissolved, such as limestone or marble. One created by tectonic activity is a fault breccia. And a new member of the family, first described from the Moon, is impact ***. This specimen, in Upper Las Vegas Wash in Nevada, is probably a fault ***.

Almandine [Garnet]

*** also known incorrectly as ***, is a species of mineral belonging to the garnet group. The name is a corruption of alabandicus, which is the name applied by Pliny the Elder to a stone found or worked at Alabanda, a town in Caria in Asia Minor. *** is an iron alumina garnet, of deep red color, inclining to purple. It is frequently cut with a convex face, or en cabochon, and is then known as carbuncle. Viewed through the spectroscope in a strong light, it generally shows three characteristic absorption bands. *** is one end-member of a mineral solid solution series, with the other end member being the garnet pyrope. The *** crystal formula is: Fe3Al2(SiO4)3. Magnesium substitutes for the iron with increasingly pyrope-rich composition.

Gypsum

*** also occurs in a massive form called alabaster, a silky mass of thin crystals called satin spar, and in clear crystals called selenite. But most *** occurs in massive chalky beds of rock ***. It's mined for the manufacture of plaster, and household wallboard is filled with ***. Plaster of Paris is a roasted *** with most of its associated water driven off, so it readily combines with water to return to ***.

Aragonite

*** and calcite are polymorphs of calcium carbonate. It is harder than calcite (3.5 to 4, rather than 3, on the Mohs scale) and somewhat denser, but like calcite it responds to weak acid by vigorous bubbling. *** occurs in two distinct places. This crystal cluster is from a pocket in a Moroccan lava bed, where it formed at high pressure and relatively low temperature. Likewise, *** occurs in greenstone during the metamorphism of deep-sea basaltic rocks. At surface conditions, *** is actually metastable, and heating it to 400°C will make it revert to calcite. The other point of interest about these crystals is that they are multiple twins that make these pseudo-hexagons. Single *** crystals are shaped more like tablets or prisms.

Epidote

*** has a Mohs hardness of 6 to 7. The color is usually enough to identify ***. If you find good crystals, they show two strongly different colors (green and brown) as you rotate them. It might be confused with actinolite and tourmaline, but it has one good cleavage where those have two and none, respectively. *** often represents alteration of the dark mafic minerals in igneous rocks such as olivine, pyroxene, amphiboles and plagioclase. It indicates a level of metamorphism between greenschist and amphibolite, particularly at low temperatures. *** thus is well known in subducted seafloor rocks. *** also occurs in metamorphosed limestones.

Limestone Oolitic

*** are whitish to cream-colored limestones composed of sand-sized (1/16 to 2 mm in size), well rounded, concentrically-layered calcite or aragonite grains called oolites (a.ka. ooliths and ooids). ***s form by rolling back and forth on a shallow seafloor, or sometimes on a shallow lakebed, by wave action. ***s are forming today on the Bahamas Platform and in Great Salt Lake, Utah. The technical geologic term for most *** limestones is "*** grainstone". Uncertainty exists about the specifics of the origin of ***s. Some researchers conclude that ***s form by completely inorganic chemical precipitation of CaCO3 from seawater around some nucleus (a tiny shell or skeletal fragment or sediment grain). Other researchers conclude that the presence of bacterial films on *** grain surfaces play a significant role in the precipitation of CaCO3 layers. However, the undoubted presence of bacteria does not necessarily indicate a biogenic origin for ***s - bacteria are everywhere.

Lepidolite

*** can be pink, yellow or gray. One notable occurrence of *** is in greisens, bodies of granite that are altered by fluorine-bearing vapors. That's what this may be, but it came from a rock shop with no data on its origin. Where it occurs in larger lumps in pegmatite bodies, *** is an ore of lithium, especially in combination with the pyroxene mineral spodumene, the other relatively common lithium mineral.

Chert

*** can form in parts of the deep sea where the tiny shells of siliceous organisms are concentrated, or elsewhere where underground fluids replace sediments with silica. *** nodules also occur in limestones. Learn more about chert.This piece of *** that I found in the Mojave Desert shows ***'s typical clean conchoidal fracture and waxy luster.*** may have a high clay content and look at first glance like shale, but its greater hardness gives it away. Also, the waxy luster of chalcedony combines with the earthy appearance of clay to give it the look of broken chocolate. *** grades into siliceous shale or siliceous mudstone. *** is a more inclusive term than flint or jasper, two other cryptocrystalline silica rocks.

Marble

*** consists of recrystallized calcite (in limestone) or dolomite (in dolomite rock). In this hand specimen of Vermont ***, the crystals are small. For fine *** of the sort used in buildings and sculpture, the crystals are even smaller. The color of *** can range from the purest white to black, ranging through the warmer colors in between depending on the other mineral impurities. Like other metamorphic rocks, *** has no fossils, and any layering that appears in it probably does not correspond to the original bedding of the precursor limestone. And like limestone, *** tends to dissolve in acidic fluids. It is quite durable in dry climates, as in the Mediterranean countries where ancient *** structures survive.

Conglomerate

*** forms in a very energetic environment, where rocks are eroded and carried downhill so swiftly that they aren't fully broken down into sand. Another name for *** is puddingstone, especially if the large clasts are well rounded and the matrix around them is very fine sand or clay. These specimens could be called puddingstone. A *** with jagged, broken clasts is usually called a breccia, and one that is poorly sorted and without rounded clasts is called a diamictite.*** is often much harder and resistant than the sandstones and shales that surround it. *** is scientifically valuable because the individual stones are samples of the older rocks that were exposed as it was forming—important clues about the ancient environment.

Malachite

*** forms in the upper, oxidized parts of copper deposits and commonly has a botryoidal habit. The intense green color is typical of copper (although chromium, nickel and iron also account for green mineral colors). It bubbles with cold acid, showing *** to be a carbonate. You'll usually see *** in rock shops and in ornamental objects, where its strong color and concentric banded structure produce a very picturesque effect. This specimen shows a more massive habit than the typical botryoidal habit that mineral collectors and carvers fancy. *** never forms crystals of any size.

Quartzite

*** forms in two different ways. In the first way, under the pressures and temperatures of deep burial, sandstone or chert recrystallizes resulting in a metamorphic rock. A *** in which all traces of the original grains and sedimentary structures are erased may also be called meta***. This Las Vegas boulder is a meta***. A *** that preserves some sedimentary features is best described as a metasandstone or metachert. The second way involves sandstone at low pressures and temperatures, where circulating fluids fill the spaces between sand grains with silica cement. This kind of ***, also calledortho***, is considered a sedimentary rock, not a metamorphic rock, because the original mineral grains are still there and bedding planes and other sedimentary structures are still evident. The traditional way to distinguish *** from sandstone is that *** fractures across or through the grains whereas sandstone splits between them.

Slate

*** forms when shale, which consists of clay minerals, is put under pressure with temperatures of a few hundred degrees or so. Then the clays begin to revert to the mica minerals from which they formed. This does two things: first, the rock grows hard enough to ring or "tink" under the hammer, and second, the rock gets a pronounced cleavage direction, so that it breaks along flat planes. Slaty cleavage is not always in the same direction as the original sedimentary bedding planes, thus any fossils originally in the rock are usually erased, but sometimes they survive in smeared or stretched form.With further metamorphism, *** turns to phyllite, then to schist or gneiss.*** is usually dark, but it can be colorful too. High-quality *** is an excellent paving stone as well as the material of long-lasting *** roof tiles and, of course, the best billiard tables. Blackboards and handheld writing tablets were once made of ***, and the name of the rock has become the name of the tablets themselves.

Sandstone

*** forms where sand is laid down and buried—beaches, dunes and seafloors. Usually *** is mostly quartz.

Andesite

*** gets its name from the Andes mountains of South America, where arc volcanic rocks mix basaltic magma with granitic crustal rocks, yielding lavas with intermediate compositions. *** is less fluid than basalt and erupts with more violence, because its dissolved gases cannot escape as easily. *** is considered the extrusive equivalent of diorite.

Sphalerite

Most often ***is reddish-brown, but it can range from black to (in rare cases) clear. Dark specimens can appear somewhat metallic in luster, but otherwise its luster can be described as resinous or adamantine. Its Mohs hardness is 3.5 to 4. It commonly occurs as tetrahedral crystals or cubes as well as in granular or massive form. *** can be found in many ore veins of sulfide minerals, commonly associated with galena and pyrite. It has excellent dodecahedral cleavage, which means that with careful hammer work you can chip it into nice 12-sided pieces.

Biotite [Mica]

*** is a common phyllosilicate mineral within the mica group, with the approximate chemical formula K(Mg,Fe). More generally, it refers to the dark mica series, primarily a solid-solution series between the iron-endmember annite, and the magnesium-endmember phlogopite; more aluminous endmembers include siderophyllite. *** was named by J.F.L. Hausmann in 1847 in honour of the French physicist Jean-Baptiste Biot, who, in 1816, researched the optical properties of mica, discovering many unique properties.*** is a sheet silicate. Iron, magnesium, aluminium, silicon, oxygen, and hydrogen form sheets that are weakly bound together by potassium ions. It is sometimes called "iron mica" because it is more iron-rich than phlogopite. It is also sometimes called "black mica" as opposed to "white mica" (muscovite) - both form in some rocks, in some instances side-by-side.

Opal

*** is a delicate mineraloid, hydrated silica or amorphous quartz. The mineral includes a fairly large amount of water molecules, and ***s should not be left in direct sunlight or high temperatures. *** is a lot more common than people think, but it's usually a thin whitish film that lines fractures in rocks subjected to diagenesis or very mild metamorphism. *** is commonly found with agate, which is cryptocrystalline quartz. Sometimes it is a bit thicker and has some internal structure that produces the highlights and color range of gem ***. Australia is where nearly all of the world's supply is mined. The colors of gem *** arise as light diffracts in the ghostly internal structure of the material. The background layer, or potch, behind the colorful part of the *** is important too. Typically, *** has a white potch, translucent potch (crystal ***) or clear potch (jelly ***).

Sodalite

*** is a feldspathoid mineral found in low-silica igneous rocks. The blue color is distinctive, but it may also be pink or white.

Limestone Travertine

*** is a form of limestone deposited by mineral springs, especially hot springs. *** often has a fibrous or concentric appearance and exists in white, tan, and cream-colored 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. *** 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.

Rhodonite

*** is a member of the pyroxenoid group of minerals, crystallizing in the triclinic system. It occurs as cleavable to compact masses with a rose-red color, often tending to brown because of surface oxidation.*** has also been worked as an ornamental stone.5.5 - 6.5 Mohs.

Albite [Plagioclase Group]

*** is a plagioclase feldspar mineral. It is the sodium endmember of the plagioclase solid solution series. As such it represents a plagioclase with less than 10% anorthite content. The pure *** endmember has the formula NaAlSi3O8. It is a tectosilicate. Its color is usually pure white, hence its name from Latin albus. It is a common constituent in felsic rocks. *** crystallizes with triclinic pinacoidal forms. Its specific gravity is about 2.62 and it has a Mohs hardness of 6 - 6.5. *** almost always exhibits crystal twinning often as minute parallel striations on the crystal face. *** often occurs as fine parallel segregations alternating with pink microcline in perthite as a result of exolution on cooling. It occurs in granitic and pegmatite masses, in some hydrothermal vein deposits and forms part of the typical greenschist metamorphic facies for rocks of originally basaltic composition.

Jasper

*** is a red, iron-rich chert that is rich in chalcedony. Many varieties are named.

Pegmatite

*** is a rock type based purely on grain size. Generally *** is defined as a rock bearing abundant interlocking crystals 3 centimeters and larger. However, most *** bodies consist largely of quartz and feldspar and are associated with granitic rocks.*** bodies are thought to form predominantly in granites during their final stage of solidification. The final fraction of mineral material is high in water and often also in elements such as fluorine or lithium. This fluid is forced to the edge of the granite pluton and forms thick veins or pods. The fluid apparently solidifies rapidly at relatively high temperatures, under conditions that favor a few very large crystals rather than many small ones. The largest crystal ever found was in a ***, a spodumene grain some 14 meters long.***s are sought out by mineral collectors and gemstone miners not only for their large crystals, but for their examples of rare minerals. The *** in this ornamental boulder near Denver, Colorado, features large books of biotite and blocks of alkali feldspar.

Galena

*** is a soft mineral of Mohs hardness of 2.5, a dark-gray streak and a high density, around 7.5 times that of water. Sometimes *** is bluish gray, but mostly it's straight gray. *** has a strong cubic cleavage that is apparent even in massive specimens. Its luster is very bright and metallic. *** forms in low- and medium-temperature ore veins, along with other sulfide minerals, carbonate minerals, and quartz. These can be found in igneous or sedimentary rocks. It often contains silver as an impurity, and silver is an important byproduct of the lead industry.

Azurite

*** is a soft, deep blue copper mineral produced by weathering of copper ore deposits. It is also known as Chessylite after the type locality at Chessy-les-Mines near Lyon, France.[2] The mineral, a carbonate, has been known since ancient times, and was mentioned in Pliny the Elder's Natural History under the Greek name kuanos (κυανός: "deep blue," root of English cyan) and the Latin name caeruleum.[4] The blue of *** is exceptionally deep and clear, and for that reason the mineral has tended to be associated since antiquity with the deep blue color of low-humidity desert and winter skies. The modern English name of the mineral reflects this association, since both *** and azure are derived via Arabic from the Persian lazhward (لاژورد), an area known for its deposits of another deep blue stone, lapis lazuli ("stone of azure").

Rose Quartz

*** is a type of quartz which exhibits a pale pink to rose red hue. Crystal form (rarely found) is called pink quartz. *** is not popular as a gem. Generally too clouded by impurities to be suitable. *** is more often carved into figures such as people or hearts. Hearts are commonly found because *** is pink and an affordable mineral.7.0 Mohs

Gneiss

*** is a typical rock type formed by regional metamorphism, in which a sedimentary or igneous rock has been deeply buried and subjected to high temperatures and pressures. Nearly all traces of the original structures (including fossils) and fabric (such as layering and ripple marks) are wiped out as the minerals migrate and recrystallize. The streaks contain minerals, like hornblende, that don't occur in sedimentary rocks. In ***, less than 50 percent of the minerals are aligned in thin, foliated layers. You can see that unlike schist, which is more strongly aligned, *** doesn't fracture along the planes of the mineral streaks. And thicker veins of large-grained minerals form in it, unlike the more evenly layered appearance of schist. With still more metamorphism, *** can turn to migmatite and then totally recrystallize into granite.Despite its highly altered nature, *** can preserve chemical evidence of its history, especially in minerals like zircon which resist metamorphism. The oldest Earth rocks known are *** from Acasta, in northern Cananda, that are more than 4 billion years old.*** makes up the largest part of the Earth's lower crust. Pretty much everywhere on the continents, you will drill straight down and eventually strike ***.

Amazonite [Microcline]

*** is an important igneous rock-forming tectosilicate mineral. It is a potassium-rich alkali feldspar. *** typically contains minor amounts of sodium. It is common in granite and pegmatites. *** forms during slow cooling of orthoclase; it is more stable at lower temperatures than orthoclase. Sanidine is a polymorph of alkali feldspar stable at yet higher temperature. *** may be clear, white, pale-yellow, brick-red, or green; it is generally characterized by cross-hatch twinning that forms as a result of the transformation of monoclinic orthoclase into triclinic ***.*** may be chemically the same as monoclinic orthoclase, but because it belongs to the triclinic crystal system, the prism angle is slightly less than right angles; hence the name "***" from the Greek "small slope." It is a fully ordered triclinic modification of potassium feldspar and is dimorphous with orthoclase. *** is identical to orthoclase in many physical properties; it can be distinguished by x-ray or optical examination; viewed under a polarizing microscope, *** exhibits a minute multiple twinning which forms a grating-like structure that is unmistakable.Perthite is either *** or orthoclase with thin lamellae of exsolved albite.Amazon stone, or amazonite, is a green variety of ***. It is not found anywhere in the Amazon Basin, however. The Spanish explorers who named it apparently confused it with another green mineral from that region.

Pumice

*** is basically lava froth, an extrusive rock frozen as its dissolved gases come out of solution. It looks solid but often floats on water. This *** specimen is from the Oakland Hills in northern California and reflects the high-silica (felsic) magmas that form when subducted marine crust mixes with granitic continental crust. *** may look solid, but it's full of small pores and spaces and weighs very little. *** is easily crushed and used for abrasive grit or soil amendments.*** is much like scoria in that both are frothy, lightweight volcanic rocks, but the bubbles in *** are small and regular and its composition is more felsic than scoria's. Also, *** is generally glassy whereas scoria is a more typical lava with microscopic crystals.

Beryl

*** is commonly found in pegmatites and is usually in well-formed crystals like this hexagonal prism. Its hardness is 8 on the Mohs scale, and it usually has the flat termination of this example. Flawless crystals are gemstones, but well-formed crystals are common at rock shops. *** can be clear as well as various colors. Clear *** is sometimes called goshenite, the bluish variety is aquamarine, red *** may sometimes be called bixbyite, green *** is better known as emerald, yellow/yellow-green *** is heliodor, and pink *** is known as morganite.

Tourmaline

*** is easy to recognize. the typical crystal shape of a nine-sided prism. typical striations along the long axis and the glassy luster. Its hardness is 7 to 7.5, its streak is white, and it has poor cleavage. *** might be mistaken for hornblende, another black glassy mineral that occurs in prisms, but hornblende forms flattened crystals (being an amphibole), is softer (5 to 6), and has a strong cleavage.*** is found in coarse-grained granite bodies, especially their late-forming pegmatite cores, and in some metamorphic rocks. In these rocks *** is the principal boron mineral, whereas in sedimentary rocks boron occurs as borates like ulexite. Clear and colored forms of ***can be attractive gemstones and fancy specimens; their chemical formulas replace Na with Ca and Fe with Mg, Al, or Li; they may also contain fluorine in place of the OH group. But all forms of *** display piezoelectricity, which means that they change their electrical properties in response to pressure. This makes *** useful in certain electrical apparatus. *** also gains an electric charge upon heating and cooling—you can watch the crystal pick up bits of paper as this happens.

Basalt

*** is fine-grained so that the individual minerals are not visible, but they include pyroxene,plagioclase feldspar and olivine. These minerals are visible in the coarse-grained, plutonic version of *** called gabbro.This specimen shows bubbles made by carbon dioxide and water vapor that came out of the molten rock as it approached the surface. During its long period of storage beneath the volcano, green grains of olivine came out of solution as well. So the bubbles, or vesicles, and the grains, or phenocrysts, represent two different events in the history of this ***.

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, *** 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, *** 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, *** becomes schist.

Goethite

*** is hydroxylated iron oxide, FeO(OH). It's responsible for brown colors in soil and is a major ingredient of rust and limonite. It's named for the scientist and poet Goethe and is a major ore of iron.

Arkose

*** is known to be young because of its content of , 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. *** usually has a reddish color from feldspar, clay and iron oxides—ingredients that are uncommon in ordinary sandstone. () *** is similar to , which is also a rock laid down near its source. But whereas graywacke forms in a seafloor setting, *** generally forms on land or near shore specifically from the rapid breakdown of . This *** specimen is of late Pennsylvanian age (about 300 million years) and comes from the Fountain Formation of central Colorado, the same stone that makes up the , south of Golden. The granite that gave rise to it is exposed directly underneath it and is more than a billion years older.

Schist Garnet

*** 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 ***osity. These larger crystals reflect light so that *** often has a high lustre, i.e. it is shiny. Porphyroblasts are common in ***, and they provide information on the temperature and pressure conditions under which the rock formed. Due to the more extreme formation conditions, *** often shows complex folding patterns. There are many varieties of *** and they are named for the dominant mineral comprising the rock, e.g. mica ***, green *** (green because of high chlorite content), garnet *** etc.

Coquina

*** is the Spanish word for cockleshells or shellfish. *** 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 *** is the extreme version. A well-cemented, strong version of *** is called coquinite. A similar rock, composed chiefly of shelly fossils that lived where they sit, unbroken and unabraded, is called a coquinoid limestone. That kind of rock is called autochthonous (aw-TOCK-thenus), meaning "arising from here." *** is made of fragments that arose elsewhere, so it is allochthonous (al-LOCK-thenus). Those are handy words in geology.

Diamond

*** is the hardest mineral, number 10 in the Mohs scale of mineral hardness. ***'s natural crystal form is an octahedron—imagine two pyramids joined base to base so their tips point opposite directions. The flat triangles on the *** correspond to the faces of the octahedron. Crystallographers call them (111) faces, and they are the hardest part of the ***. *** crystals usually have rounded, grooved edges as can be seen next to the flat faces. *** has an unusual adamantine luster, a brilliant, almost metallic surface appearance that, along with its extreme hardness, distinguishes *** from all other minerals. Quartz is softer and has a glassy luster. The word "adamantine" refers to another ancient name for ***, adamant. Today adamant does not signify *** but extreme, ***like hardness. ***s form at great depth, well below the crust. Normal geologic processes bring ***s to the surface too slowly to avoid retrograde metamorphism, which turns ***s into graphite. They're able to reach the surface only in peculiar eruptions that explode into the air, leaving behind bottomless pipes of mantle rocks called kimberlites. ***s occur in a range of forms, from nearly perfect crystals to rough grains to warty black lumps known as bort. All forms of *** are valuable, either as gems or as superhard grinding and cutting grit. Gem ***s are used for their hardness and transparency in the *** anvil cell, an apparatus that puts mineral samples under high pressures and temperatures.

Topaz

*** is the hardest silicate mineral, along with beryl. It is usually found in high-temperature tin-bearing veins, in granites, in gas pockets in rhyolite, and in pegmatites. *** is tough enough to endure the pounding of streams, where *** pebbles can occasionally be found.Its hardness, clarity, and beauty make*** a popular gemstone, and its well-formed crystals make *** a favorite of mineral collectors. Most pink ***, especially in jewelry, are heated to create that color.

Talc

*** is the softest mineral, the standard for hardness grade 1 in the Mohs scale. Your fingernail will easily scratch it. *** has a greasy feel and a translucent, soapy look. *** and pyrophyllite are very similar, but pyrophyllite (which has Al instead of Mg) may be slightly harder. This talc specimen comes from somewhere in New York, but ***is quarried throughout the eastern United States, wherever magnesian silicate rocks or dolomite undergoes alteration (steatitization). *** is very useful, and not just because it can be ground into talcum powder—it's a common filler in paints, rubber and plastics too. Other less precise names for *** are steatite or soapstone, but those are rocks containing impure *** rather than the pure mineral.

Corundum

*** is the standard for hardness 9 in the Mohs hardness scale. *** occurs in rocks that are low in silica, particularly in nepheline syenite, schists altered by alumina-bearing fluids, and altered limestones. It's also found in pegmatites. A fine-grained natural mixture of *** and magnetite is called emery, which was once a widely used mineral for abrasives. Pure *** is a clear mineral. Various impurities give it brown, yellow, red, blue and violet colors. In gem-quality stones, all of these except for red are called sapphire. Red *** is called ruby. That's why you cannot buy a red sapphire! *** gemstones are well known for the property of asterism, in which aligned microscopic inclusions create the appearance of a "star" in a round cabachon-cut stone. ***, in the form of industrial alumina, is an important commodity. Alumina grit is the working ingredient of sandpaper, and sapphire plates and rods are used in many high-tech applications. However, all of these uses, as well as most *** jewelry, employ manufactured rather than natural *** today.

Rhyolite

*** is typically dark and has a glassy groundmass. This is a less typical white example; it can also be reddish. Being high in silica, *** is a stiff lava that tends to have a banded appearance. Indeed, "***" means "flow stone" in scientific Greek.*** is typically found in continental settings where magmas have incorporated granitic rocks from the crust as they rise from the mantle. It tends to make lava domes when it erupts.

Calcite

*** is used to define hardness 3 in the Mohs scale of mineral hardness. Your fingernail is about hardness 2½, so you can't scratch ***. It usually forms dull-white, sugary-looking grains but may take on other pale colors. If its hardness and its appearance aren't enough to identify ***, the acid test, in which cold dilute hydrochloric acid (or white vinegar) produces bubbles of carbon dioxide on the mineral's surface, is the definitive test. *** is a very common mineral in many different geologic settings; it makes up mostlimestone and marble, and it forms most cavestone formations like stalactites. Often *** is the gangue mineral, or worthless part, of ore rocks. But clear pieces like this "Iceland spar" specimen are less common. Iceland spar is named after classic occurrences in Iceland, where fine *** specimens can be found as big as your head. This is not a true crystal, but a cleavage fragment. *** is said to have rhombohedral cleavage, because each of its faces is a rhombus, or warped rectangle in which none of the corners are square. When it forms true crystals, *** takes platy or spiky shapes that give it the common name "dogtooth spar." If you look through a piece of ***, objects behind the specimen are offset and doubled. The offset is due to refraction of the light traveling through the crystal, just as a stick appears to bend when you stick it partway into water. The doubling is due to the fact that light is refracted differently in different directions within the crystal. *** is the classic example of double refraction, but it's not that rare in other minerals.

Gold

*** is usually alloyed with some copper as well as other noble metals like silver, platinum and palladium. *** rarely accumulates into big pieces. If you find one, its heaviness and distinctive yellow streak serve to identify it. In fact, a streak plate or touchstone has been used for centuries to assess the purity of ***. *** nuggets account for very little of the world's gold production. The *** ore being mined today shows no sign of its valuable fraction, yielding a few grams in every ton of rock. Large mines in Nevada, South Africa, Australia, Canada, and the former Soviet Union supply the world with *** for hundreds of industrial uses, bullion, dentistry, coinage, and jewelry. *** is prized for its electrical conductivity, resistance to corrosion, and extreme malleability. Your computer has *** contacts in it.

Fluorite

*** isn't the most common halide—common salt or halite takes that title—but you'll find it in every rockhound's collection. *** forms at shallow depths and relatively cool conditions where deep fluorine-bearing fluids, like the last juices of plutonic intrusions or the strong brines that deposit ores, invade sedimentary rocks with lots of calcium, like limestone. Thus *** is not an evaporite mineral. Mineral collectors prize *** for its very wide range of colors, but it's best known for purple. It also often shows different fluorescent colors under ultraviolet light. And some fluorite specimens display thermoluminescence, emitting light as they are heated. No other mineral displays so many kinds of visual interest. *** also occurs in several different crystal forms. It's the standard for hardness 4 in the Mohs scale.

Diatomite

*** may resemble chalk or fine-grained volcanic ash beds. But pure *** 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. Diatoms are one-celled plants that secrete shells out of silica that they extract from the water around them. The shells, called frustules, are intricate and beautiful glassy cages made of opal. Most diatom species live in shallow water, either fresh or salt. *** is very useful because silica is strong and chemically inert. It's widely used to filter water and other industrial liquids including foods. It makes excellent fireproof lining and insulation for things like smelters and refiners. It's a very common filler material in paints, foods, plastics, cosmetics, papers and much more. *** is part of many concrete blends and other building materials. In powdered form it's called diatomaceous earth or DE, which you can buy as a safe insecticide—the microscopic shells injure insects but are harmless to pets and people.

Tremolite

*** occurs as grey, green or lavender to pink stout elongated crystals, which form fibrous, granular or columnar aggregates. They are known as fine needle-like inclusions in quartz or emerald. The needles produce a distinct cat's eye effect in cabochons cut from compact green ***from Ontario, Canada.

Dolostone

*** or *** is a sedimentary carbonate rock that contains a high percentage of the mineral dolomite. In old U.S.G.S. publications it was referred to as magnesian limestone. Most *** formed as a magnesium replacement of limestone or lime mud prior to lithification.[1] It is resistant to erosion and can either contain bedded layers or be unbedded. It is less soluble than limestone in weakly acidic groundwater, but it can still develop solution features over time. The term *** was introduced to avoid confusion with the mineral dolomite. The usage of the term *** is controversial because the name dolomite was first applied to the rock during the late 18th century and thus has technical precedence. The use of the term *** is not recommended by the Glossary of Geology published by theAmerican Geological Institute. It is, however, used in some geological publications

Bituminous Coal

*** or black coal is a relatively soft coal containing 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. Its coloration can be black or sometimes dark brown; often there are well-defined bands of bright and dull material within the seams. These distinctive sequences, which are classified according to either "dull, bright-banded" or "bright, dull-banded", is how ***s are stratigraphically identified.*** is an organic sedimentary rock formed by diagenetic and sub metamorphic compression of peat bog material. Within the coal mining industry, this type of coal is known for releasing the largest amounts of firedamp, a dangerous mixture of gases that can cause underground explosions. Extraction of *** demands the highest safety procedures involving attentive gas monitoring, good ventilation and vigilant site management.

Limestone Chalk

*** s a soft, white, porous sedimentary rock, a form of limestone composed of the mineral calcite. Calcite is calcium carbonate or CaCO3. It forms under reasonably deep marine conditions from the gradual accumulation of minute calcite plates (coccoliths) shed from micro-organisms called coccolithophores. It is common to find chert or flint nodules embedded in ***. *** can also refer to other compounds including magnesium silicate and calcium sulfate. "Nitzana *** curves" situated at Western Negev, Israel are *** deposits formed at the Mesozoic era's Tethys Ocean . *** has greater resistance to weathering and slumping than the clays with which it is usually associated, thus forming tall steep cliffs where *** ridges meet the sea. *** hills, known as *** downland, usually form where bands of *** reach the surface at an angle, so forming a scarp slope. Because *** is porous it can hold a large volume of ground water, providing a natural reservoir that releases water slowly through dry seasons. Due to its porosity *** is studied in numerous geophysical experiments (reflection seismology). In the North Sea, experiments have been performed for "evaluating 4D seismic for the correct pore pressure prediction", through the "stress coefficient of **

Bornite

*** stands out for the amazing metallic blue-green color it turns after exposure to the air. That gives *** the nickname peacock ore. ***has a Mohs hardness of 3 and a dark gray streak. Copper sulfides are a closely related mineral group, and they often occur together.

Hematite

*** takes on several different appearances, but it's most easily identified when it is black, heavy and hard. It has a hardness of 6 on the Mohs scale and a distinctive red-brown streak. Unlike its oxide cousin magnetite, *** does not attract a magnet except very weakly. *** is common in soil and sedimentary rocks, accounting for their reddish colors. *** is also the principal iron mineral in banded iron formation. This specimen of "kidney ore" *** displays the reniform mineral habit.

Sulfur

*** the element S, usually occurs combined in minerals, but the native form is common around volcanoes and in thick underground beds. *** is predominantly found in sulfide minerals like pyrite and sulfate minerals like gypsum. But the element is volatile and is released in vapor around volcanoes. *** gas originates as hydrogen sulfide (H2S), but that quickly oxidizes to sulfuric acid (H2SO4) and enters the water cycle, eventually to combine with metal ions and become a sulfide or sulfate mineral, ready for liberation again by a future volcano. A fraction of this***, though, is preserved in native form, either briefly around gas vents like this beautiful example from White Island Volcano in New Zealand, or in thick beds underground that form by chemical reduction. Nowadays, *** is a byproduct of metal mining and petroleum production.

Chalcopyrite

*** usually occurs in massive form rather than in crystals, but its crystals are unusual among the sulfides in having a shape like a four-sided pyramid (technically they are scalenohedra). It has a Mohs hardness of 3.5 to 4, a metallic luster, a greenish black streak and a golden color that is commonly tarnished in various hues (though not the brilliant blue of bornite). *** is softer and yellower than pyrite, more brittle than gold. It is often mixed with pyrite.

Granite

***" is used by the public as a catch-all name for any light-colored, coarse-grained igneous rock. The geologist examines these in the field and calls them granitoids pending laboratory tests. The key to true *** is that it contains sizable amounts of quartz and both kinds of feldspar.

Staurolite

***, (Fe,Mg)4Al17(Si,Al)8O45(OH)3, occurs in medium-grade metamorphic rocks mica schist in brown crystals. *** is fairly hard, measuring 7 to 7.5 on the Mohs scale, and is used as an abrasive mineral in sandblasting.

Bauxite

***, an aluminium ore, is the world's main source of aluminum. It consists mostly of the minerals gibbsite Al(OH)3, boehmite γ-AlO(OH) and diaspore α-AlO(OH), mixed with the two iron oxides goethite and haematite, the clay mineral kaolinite and small amounts of anatase TiO2. *** was named by the Frenchgeologist Pierre Berthier in 1821 after the village of Les Baux in Provence, southern France, where he discovered it and was the first to recognize that it contained aluminium.

Lignite Coal

***, often referred to as brown coal, is a soft brown combustible sedimentary rock that is formed from naturally compressed peat. It is considered the lowest rank of coal due to its relatively low heat content. It is mined in Bulgaria,Kosovo Greece, Germany, Poland, Serbia, Russia, the United States, Canada, India,Australia and many other parts of Europe and it is used almost exclusively as a fuel for steam-electric power generation. 25.7% of Germany's electricity comes from *** power plants,[1] while in Greece *** provides about 50% of its power needs.

Amethyst

***, the purple variety of quartz, gets its color from iron atoms in the crystal matrix plus the presence of "holes," where atoms are missing.

Schist Mica

A *** is defined as "a metamorphic crystalline rock that has a closely foliated structure and can be split along approximately parallel planes." In layman terms, this means it is made up of many layers and if this rock is struck it will break along a particular cleavage; thus the word *** is derived from the Greek word meaning 'to split'. Manhattan ***, otherwise known as Cambrian Manhattan Formation, is the second oldest of the five bedrock layers in NYC and is found mostly in upper and lower Manhattan. The oldest is Fordham gneiss found in the Bronx, and the other three bedrocks are Hartland formation in Brooklyn, Queens, the Bronx, and Manhattan; Staten Island serpentinite in Staten Island; and Inwood marble in all of Manhattan and beneath the Hudson and East Rivers.This *** was formed about 450 million years ago when shale was pushed from the ocean floor into the Earth's molten core during a collision between North America and the Atlantic Ocean. While there, it was transformed by heat and pressure into various minerals including quartz, feldspar, hornblende, and ***. The heat and pressure is what created the metamorphic rock known as ***, and this particular variation contains ***. It is also sedimentary because it is composed of various layers.*** itself has many uses in the commercial world, such as electrical insulation, in rockets, and in other environments that require high temperatures. The *** *** bedrock also plays an important role in where the skyscrapers of Manhattan are constructed. The ground is more stable where the *** is closer to the surface, which explains why the taller buildings are more densely clustered in the Midtown area.

Hornblende

A long, dark mineral with abundant cleavage faces in a granitic rock is hornblende more often than not. The chemical makeup of hornblende is quite variable, so its formula is ugly: (Ca,Na)2-3(Mg,Fe+2,Fe+3,Al)5(OH)2[(Si,Al)8O22]. Hornblende is usually black but can also be dark green or brown. It is a common primary mineral in granitic rocks and a common metamorphic mineral in gneiss and schist.

Quartz [Agate/Onyx]

Agate is the banded form of the mineral Chalcedony, which is a microcrystalline variety of Quartz. Agate is the most varied and popular type of Chalcedony, having many varieties on its own. Although the pattern on every Agate is unique, the locality of an Agate will provide resemblances in banding style and color, thus lending many Agates with a geographic prefix. Some examples are Laguna Agate (named after Ojo Laguna, Mexico) or Botswana Agate (after the African country of Botswana). Other variety names used connote specific colors or patterns, such as Fire Agate or Eye Agate.Agate usually forms in rounded nodules or knobs which need to be sliced open to bring out the internal pattern hidden in the stone. Most Agate is ugly in its natural state; specimens must be polished to bring out their full beauty. Much of the Agate sold to collectors has been treated, in the form of tumbled stones or polished slabs. Popular collector forms of Agate include nodules or geodes sliced in the middle into two polished cross-sections, or thin slabs from nodule or geode cross-sections.The formation of Agate is most often from deposition of layers of silica filling voids in volcanic vesicles or other cavities. The layers form in stages with some of new layers providing an alternating color. Since the cavities are irregularly and uniquely shaped, each Agate forms its own pattern based on the original cavity shape. When a cavity is completely filled, it forms a solid mass of Agate, but often it is only partially filled, leaving a hollow void which often has crystalline Quartz growths on its innermost layer. This is the cause of Agate forming the outer lining of most geodes. Agate is often dyed to enhance its colors. This is especially true of Agate from Brazil. Bright neon colors such as bright blue and red are rarely natural. Agate is named after the Achates River (now known as the Dirillo River) on the island of Sicily, Italy, whose upper waters were an ancient source of this gemstone.

Quartz [Chalcedony]

Chalcedony is not scientifically its own mineral species, but rather a form of Quartz in microcrystalline form. However, the name is an old name, and almost all mineral reference guides and collectors distinguish Chalcedony separately from Quartz. In the gem trade, the name Chalcedony usually describes only white or blue Chalcedony, to distinguish it from the multicolored banded variety Agate and other unique varieties of this mineral. Chalcedony is quite varied in its formation habits. It sometimes occurs in geodes, lining the cavity with mammilary blobs. Its Agate variety is also found in geodes, commonly lining the outer layer underneath the larger Quartz crystals. Chalcedony also forms pseudomorphs after organic material. A well-known example is petrified wood, in which the wood has been completely transformed into Chalcedony. In the Petrified Forest National Monument in Arizona, an entire forest was transformed into petrified wood. Remains of this ancient forest can be seen in the huge silicafied logs that are found in the area.Another well-known pseudomorph is Chalcedony after coral. In the Tampa Bay in Florida, coral has been chemically replaced by Chalcedony, and its original form is preserved. Another famous Chalcedony pseudomorph is Tiger's Eye. This popular variety has very unique optical properties in the form of a bronze sheen that is caused by the fibrous mineral Crocidolite that was chemically replaced into Chalcedony through pseudomorphism.Impurities are frequently present in Chalcedony. They may form a moss like growth in the mineral, forming what is known as Moss Agate. Another example is Dendritic Agate, a variety of Chalcedony containing manganese oxide impurities that form fabrications resembling trees. These forms of Agate are not true Agates, since they lack the banding.

Barite

In the loose sandstones of Oklahoma, *** forms "roses". They're similar to gypsum roses, and sure enough, gypsum is also a sulfate mineral. *** is much heavier, though; its specific gravity is around 4.5 (by comparison, that of quartz is 2.6) because barium is an element of high atomic weight. Otherwise, *** is hard to tell apart from other white minerals with tabular crystal habits. *** also occurs in a botryoidal habit. *** is widely used in the drilling industry as a dense slurry—drilling mud—that supports the weight of the drill string. It also has medical uses as a filling for body cavities that is opaque to x-rays. The name means "heavy stone" and it's also known by miners as cawk or heavy spar.

Kaolinite

Kaolinite (/ˈkeɪəlɨˌnaɪt/) is a clay mineral, part of the group of industrial minerals, with the chemical composition Al2Si2O5(OH)4. It is a layered silicate mineral, with one tetrahedral sheet linked through oxygen atoms to one octahedral sheet of alumina octahedra.[4] Rocks that are rich in kaolinite are known as kaolin or china clay.[5]The name is derived from Chinese Kao-Ling (高岭/高嶺, pinyin Gāolǐng), a village near Jingdezhen, Jiangxi province, China.[6] The name entered English in 1727 from the French version of the word: kaolin, following Francois Xavier d'Entrecolles's reports from Jingdezhen.[7] In Africa, kaolin is sometimes known as kalaba (in Gabon[8] and Cameroon[9]), calaba, and calabachop (in Equatorial Guinea).Kaolinite has a low shrink-swell capacity and a low cation exchange capacity (1-15 meq/100 g). It is a soft, earthy, usually white mineral (dioctahedral phyllosilicate clay), produced by the chemical weathering of aluminium silicate minerals like feldspar. In many parts of the world, it is colored pink-orange-red by iron oxide, giving it a distinct rust hue. Lighter concentrations yield white, yellow or light orange colors. Alternating layers are sometimes found, as at Providence Canyon State Park in Georgia, United States. Commercial grades of kaolin are supplied and transported as dry powder, semi-dry noodle or as liquid slurry.

Dolomite

Many deposits of limestone are altered to some extent into *** rock. The details are still a subject of research. *** also occurs in some bodies of serpentinite, which are rich in magnesium. It forms at the Earth's surface in a few very unusual places marked by high salinity and extreme alkaline conditions.*** is harder than calcite (Mohs hardness 4). It often has a light pinkish color, and if it forms crystals these often have a curved shape. It commonly has a pearly luster. The crystal shape and luster may reflect the atomic structure of the mineral, in which two cations of very different sizes—magnesium and calcium—place stress on the crystal lattice. However, commonly the two minerals appear so much alike that the acid test is the only quick way to distinguish them. You can see the rhombohedral cleavage of *** in the center of this specimen, which is typical of carbonate minerals. Rock that is primarily *** is sometimes called dolostone, but "***" or "*** rock" are preferred names. In fact, the rock *** was named before the mineral that composes it.

Muscovite [Mica]

Muscovite (also known as common mica, isinglass, or potash mica[4]) is a phyllosilicate mineral of aluminium and potassium with formula KAl2(AlSi3O10)(F,OH)2, or (KF)2(Al2O3)3(SiO2)6(H2O). It has a highly-perfect basal cleavage yielding remarkably-thin laminæ (sheets) which are often highly elastic. Sheets of muscovite 5×3 m have been found in Nellore, India.Muscovite has a Mohs hardness of 2-2.25 parallel to the face, 4 perpendicular to the [001] and a specific gravity of 2.76-3. It can be colorless or tinted through grays, browns, greens, yellows, or (rarely) violet or red, and can be transparent or translucent. It is anisotropic and has high birefringence. Its crystal system is monoclinic. The green, chromium-rich variety is called fuchsite; mariposite is also a chromium-rich type of muscovite.Muscovite is the most common mica, found in granites, pegmatites, gneisses, and schists, and as a contact metamorphic rock or as a secondary mineral resulting from the alteration of topaz, feldspar, kyanite, etc. In pegmatites, it is often found in immense sheets that are commercially valuable. Muscovite is in demand for the manufacture of fireproofing and insulating materials and to some extent as a lubricant.The name muscovite comes from Muscovy-glass, a name given to the mineral in Elizabethan England due to its use in medieval Russia as a cheaper alternative to glass in windows. This usage became widely known in England during the sixteenth century with its first mention appearing in letters by George Turberville, the secretary of England's ambassador to the Russian tzar Ivan the Terrible, in 1568.