Rocks and Minerals

Silver

Soft white metal and usually occurs as a minor constituent in the ores of other metals. Is a precious metal due to its rarity and economic value. Electrical and thermal conductance that is higher than any other metal. Higher reflectivity at most temperatures than any other metal, attractive color and luster that resist tarnish and make the metal desirable in jewelry, coins, tableware, etc. Family: Native Formula: Ag Color: silvery white Habit: thin flakes, paltes, and dendritic crystal clusters formed in the narrow spaces of joints and fractures. filiform and wire like habits are also seen. Crystal system: isometric Streak: silvery white Luster: metallic Crystal Structure: Cleavage: none Fracture: Tenacity: Hardness: 2.5 - 3 SG: 10-11 Diaphaneity: opaque Formation: Other: Rarely found as a native element mineral. rarely found in significant amounts in placer deposits. Native sometimes found in the oxidized zones avoce the ores of other metals. Silver does not readily reacnt with oxygen or water, reacts with hydrogen sulfide to produce a tarnished surface that is composed of acantite. Most native silver found associated with hydrothermal activity, often occurs in abudafce as veins and cavity fillings. Most gold found in placer deposits is alloyed with small amounts of silver. If the ratio between gold and silver reaches at least 20% silver, the material is called "electrum." Electrum is the name for an alloy of gold and silver. A significant amount of today's silver production is a refining byproduct of gold mining. Most of the silver produced today is a byproduct of mining copper, lead, and zinc. The silver occurs within the ores of these metals in one of two ways: 1) substituting for one of the metal ions within the ore mineral's atomic structure; or, 2) occurring as an inclusion of native silver or a silver mineral within the ore mineral. The value of this minor silver within the ore mineral can exceed the value of the primary metal within the ore. Uses in jewelry, tableware, coins, electronics, photographic films, ornaments

Hematite

The most important ore of iron. Pigment, heavy media separation, radiation shielding, ballast, polishing compounds, a minor gemstone. Common rock-forming mineral found in sedimentary, metamorphic, and igneous rocks. Despite variable appearance always has a reddish streak. Family: Oxide Formula: Fe2O3 Color: Black to steel-gray to silver; red to reddish brown to black Habit: micaceous, massive, crystalline, botryoidal, fibrous, oolitic, and others. Crystal system: Trigonal Streak: Red to reddish brown Luster: metallic, submetallic, earthy Crystal Structure: Cleavage: none Fracture: Tenacity: Hardness: 5-6.5 SG: 5-5.3 Diaphaneity: opaque Formation: Pure hematite has a composition of about 70% iron and 30% oxygen by weight. Like most natural materials, it is rarely found with that pure composition. This is particularly true of the sedimentary deposits where hematite forms by inorganic or biological precipitation in a body of water. primary mineral and as an alteration product in igneous, metamorphic, and sedimentary rocks. It can crystallize during the differentiation of a magma or precipitate from hydrothermal fluids moving through a rock mass. It can also form during contact metamorphism when hot magmas react with adjacent rocks. The most important hematite deposits formed in sedimentary environments. About 2.4 billion years ago, Earth's oceans were rich in dissolved iron, but very little free oxygen was present in the water. Then a group of cyanobacteria became capable of photosynthesis. The bacteria used sunlight as an energy source to convert carbon dioxide and water into carbohydrates, oxygen, and water. This reaction released the first free oxygen into the ocean environment. The new oxygen immediately combined with the iron to form hematite, which sank to the bottom of the seafloor and became the rock units that we know today as the banded iron formations. Soon, photosynthesis was occurring in many parts of Earth's oceans, and extensive hematite deposits were accumulating on the seafloor. This deposition continued for hundreds of millions of years - from about 2.4 to 1.8 million years ago. This allowed the formation of iron deposits hundreds to several thousand feet thick that are laterally persistent over hundreds to thousands of square miles. They comprise some of the largest rock formations in Earth's rock record. Other: By itself is not magnetic but if it contains enough magnetite then it may seem that way. Many of the sedimentary iron deposits contain both hematite and magnetite as well as other iron minerals. These are often in intimate association, and the ore is mined, crushed, and processed to recover both minerals.Minor clastic sedimentation can add clay minerals to the iron oxide. Episodic sedimentation can cause the deposit to have alternating bands of iron oxide and shale. Silica in the form of jasper, chert, or chalcedony can be added by chemical, clastic, or biological processes in small amounts or in significant episodes. These layered deposits of hematite and shale or hematite and silica have become known as the "banded iron formations" (see image). Hematite is one of the most abundant minerals in the rocks and soils on the surface of Mars, gives the landscape a reddish-brown color.

Dolomite

Thin, platy cream-colored crystals possibly has black specks between crystals. Differentiate from calcite using hardness and reaction to acid. Family: Carbonate Formula: CaMg(CO3)2 Color: White, grey to pink, reddish-white, brownish-white; colorless in transmitted light, Small amounts of iron in the structure give the crystals a yellow to brown tint. Manganese substitutes in the structure also up to about three percent MnO. A high manganese content gives the crystals a rosy pink color. Habit: Tabular crystals, often with curved faces, also columnar, stalactitic, granular, massive Crystal system: Trigonal Streak: White Luster: Vitreous to pearly Crystal Structure: Cleavage: 3 directions of cleavage not at right angles Fracture: conchoidal Tenacity: brittle Hardness: 3.5-4 SG: 2.84-2.86 Diaphaneity: transparent to translucnet Formation: found to occur under anaerobic conditions in supersaturated saline lagoons Other: Lead, zinc, and cobalt also substitute in the structure for magnesium. Used for acid neutralization in the chemical industry, in stream restoration projects, and as a soil conditioner. Dolomite is used as a source of magnesia (MgO), a feed additive for livestock, a sintering agent and flux in metal processing, and as an ingredient in the production of glass, bricks, and ceramics. Dolomite serves as the host rock for many lead, zinc, and copper deposits. These deposits form when hot, acidic hydrothermal solutions move upward from depth through a fracture system that encounters a dolomitic rock unit. These solutions react with the dolomite, which causes a drop in pH that triggers the precipitation of metals from solution. Dolomite also serves as an oil and gas reservoir rock. During the conversion of calcite to dolomite, a volume reduction occurs. This can produce pore spaces in the rock that can be filled with oil or natural gas that migrate in as they are released from other rock units. This makes the dolomite a reservoir rock and a target of oil and gas drilling.

Aventurine

a form of quartz, characterised by its translucency and the presence of platy mineral inclusions that give it a shimmering or glistening effect termed aventurescence. Family: Silicate Formula: SiO2 Color: Usually green. Also orange, yellow, red, pink, purple, white, brown, and blue. Habit: Crystal system: hexagonal Streak: colorless Luster: vitreous, aventuresecnt Cleavage: Fracture: Tenacity: Hardness: 6.5-7 SG: 2.6-2.7 Diaphaneity: Formation: Other: most common color of aventurine is green, but it may also be orange, brown, yellow, blue, or grey. Chrome-bearing fuchsite (a variety of muscovite mica) is the classic inclusion and gives a silvery green or blue sheen. Oranges and browns are attributed to hematite or goethite Green aventurine is a common material used to produce beads and cabochons. These are used to make earrings, pendants, rings, and other jewelry. Aventurine and translucent quartz without aventurescence are often dyed bright colors. Dye is used to produce low-cost cabochons with bright colors that are often seen in inexpensive jewelry.

Pyromorphite

a member of the Apatite group, a group of isomorphous hexagonal minerals. It is very similar in structure and appearance to Mimetite, and may be partially replaced by it. In fact, sometimes Pyromorphite and Mimetite are virtually indistinguishable from each other and may be wrongly labeled as the other. It is part of a series with two other minerals: mimetite (Pb5(AsO4)3Cl) and vanadinite (Pb5(VO4)3Cl), the resemblance in external characters is so close that, as a rule, it is only possible to distinguish between them by chemical tests. They were formerly confused under the names green lead ore and brown lead ore. The name is derived from the Greek for pyr (fire) and morfe (form) due to its crystallization behavior after being melted. Family: Phosphate, Apatite group Formula: Pb5(PO4)3Cl Color: Dark green to grass-green or green, yellow, yellow-orange, reddish orange, yellow-brown, greenish-yellow or yellowish-green, shades of brown, tan, grayish, white and may be colorless; colourless or faintly tinted in transmitted light Habit: prismatic to acicular crystals, globular to reniform . Occurs as barrel-like hexagonal crystals, which are usually grouped together in interesting aggregates, and may be bipyramidal. Also acicular, crusty, grainy, radiating, reniform, botryoidal and in curvy aggregates. Some larger crystals may be hollowed out on the ends or have a hopper growth pattern.Crystal system: hexagonal Streak: white Luster: resinous to subadamantine Cleavage: imperfect Fracture: uneven to sub conchoidal Tenacity: brittle Hardness: 3.5-4 SG: 7.04 measured, 7.14 calculated Diaphaneity: transparent to translucent Formation: As a secondary mineral in the oxidation zone of lead ore deposits. Other: Dissolves in nitric acid. Pyromorphite is a minor ore of lead where it occurs with more abundant lead minerals. It is also a popular mineral among collectors, especially specimens from classic occurrences, as well as newer finds of bright neon green Pyromorphite which command very high prices.

Pyrite

"Fool's Gold." The mineral's gold color, metallic luster, and high specific gravity often cause it to be mistaken for gold by inexperienced prospectors. However, pyrite is often associated with gold. The two minerals often form together, and in some deposits pyrite contains enough included gold to warrant mining. Family: sulfide Formula: FeS2 Color: Brass yellow - often tarnished to brass Habit: Crystal system: isometric Streak: greenish black to brownish black Luster: metallic Cleavage: breaks with a conchoidal fracture Fracture: Tenacity: Hardness: 6-6.5 SG: 4.9-5.2 Diaphaneity: opaque Formation: most common sulfide mineral. It forms at high and low temperatures and occurs, usually in small quantities, in igneous, metamorphic, and sedimentary rocks worldwide. Pyrite is so common that many geologists would consider it to be a ubiquitous mineral. Other: The name "pyrite" is after the Greek "pyr" meaning "fire." This name was given because pyrite can be used to create the sparks needed for starting a fire if it is struck against metal or another hard material. Pieces of pyrite have also been used as a spark-producing material in flintlock firearms. Pyrite used to be an important ore for the production of sulfur and sulfuric acid. Today most sulfur is obtained as a byproduct of oil and gas processing. Some sulfur continues to be produced from pyrite as a byproduct of gold production. The most important use of pyrite is as an ore of gold. Gold and pyrite form under similar conditions and occur together in the same rocks. In some deposits small amounts of gold occur as inclusions and substitutions within pyrite. Crushed stone used to make concrete, concrete block, and asphalt paving materials must be free of pyrite. Pyrite will oxidize when it is exposed to air and moisture. That oxidation will result in the production of acids and a volume change that will damage the concrete and reduce its strength. This damage can result in failure or maintenance problems. The conditions of pyrite formation in the sedimentary environment include a supply of iron, a supply of sulfur, and an oxygen-poor environment. This often occurs in association with decaying organic materials. Organic decay consumes oxygen and releases sulfur. For this reason, pyrite commonly and preferentially occurs in dark-colored organic-rich sediments such as coal and black shale. The pyrite often replaces organic materials such as plant debris and shells to create interesting fossils composed of pyrite.

Beryl

a minor ore of beryllium, and color varieties of the mineral are among the world's most popular gemstones. Emerald, aquamarine, heliodor, and morganite are the most popular varieties Family: Silicate Formula: Be3Al2Si6O18 Color: Green, yellow, blue, red, pink, orange, colorless Habit: Crystal system: Hexagonal Streak: colorlesss Luster: vitreous Cleavage: imperfect Fracture: Tenacity: Hardness: 7.5-8 SG: 2.6-2.8 Diaphaneity: transparent to translucent Formation: contains a significant amount of beryllium. Beryllium is a very rare metal, and that limits the formation of beryl to a few geological situations where beryllium is present in sufficient amounts to form minerals. It mainly occurs in granite, rhyolite, and granite pegmatites; in metamorphic rocks associated with pegmatites; and, in veins and cavities where hydrothermal activity has altered rocks of granitic composition. These different types of deposits are often found together and serve as an exploration indicator for finding beryl. Beryl is also found where carbonaceous shale, limestone, and marble have been acted upon by regional metamorphism. The famous emerald deposits of Colombia and Zambia were formed under these conditions. The carbonaceous material is thought to provide the chromium or vanadium needed to color the emerald. Other: Beryl once served as the world's only important ore of beryllium metal. But in 1969, Spor Mountain, Utah became the source for about 80% of the world's beryllium supply when bertrandite, a beryllium silicate hydroxide mineral, was discovered there. The extraction of beryllium from beryl is very costly, and as long as bertrandite is available in large amounts, beryl will remain a minor ore of that metal. Small amounts of beryl, mostly produced as a by-product of gemstone mining, are still used to produce beryllium. The most important use of beryl today is as a gemstone. It is one of the most important gem minerals, and the gems of beryl are named by their color as: emerald (green), aquamarine (greenish blue to blue), morganite (pink to orange), red beryl (red), heliodor (yellow to greenish yellow), maxixe (deep blue), goshenite (colorless), and green beryl (light green). Synthetic beryl has been commercially manufactured for gemstone use since the 1930s. Synthetic beryls have the same chemical composition and physical properties as natural beryl. They can be fashioned into gemstones that rival the beauty of natural gems and can be sold for a much lower cost. Many people opt for a synthetic emerald because it can have a superior color, superior clarity, greater durability, and a much lower cost than a natural gem.

Agate

Agate is one of the most common materials used in the art of hardstone carving, and has been recovered at a number of ancient sites, Family: Silicate Formula: SiO2 Color: brown, white, red, gray, pink, black, and yellow. The colors are caused by impurities and occur as alternating bands within the agate. The different colors were produced as groundwaters of different compositions seeped into the cavity. The banding within a cavity is a record of water chemistry change. This banding gives many agates the interesting colors and patterns that make it a popular gemstone Habit: Crystal system: Streak: white Luster: waxy, dull Cleavage: none Fracture: conchoidal, subschoncoidal Tenacity: brittle Hardness: 6.5-7 SG: 2.6 Diaphaneity: Formation: generally forms by the deposition of silica from groundwater in the cavities of igneous rocks. The agate deposits in concentric layers around the walls of the cavity, or in horizontal layers building up from the bottom of the cavity. These structures produce the banded patterns that are characteristic of many agates. Some of these cavities are lined with crystals and those are known as geodes. Other: Lace agate is a variety that exhibits a lace-like pattern with forms such as eyes, swirls, bands or zigzags. Moss agate, as the name suggests, exhibits a moss-like pattern and is of a greenish colour. The coloration is not created by any vegetative growth, but rather through the mixture of chalcedony and oxidized iron hornblende. Dendritic agate also displays vegetative features, including fern-like patterns formed due to the presence of manganese and iron oxides.[14] Turritella agate (Elimia tenera) is formed from the shells of fossilized freshwater Turritellas, gastropods with elongated spiral shells. Similarly, coral, petrified wood, porous rocks and other organic remains can also form agate.[15] Coldwater agates, such as the Lake Michigan cloud agate, did not form under volcanic processes, but instead formed within the limestone and dolomite strata of marine origin. Like volcanic-origin agates, Coldwater agates formed from silica gels that lined pockets and seams within the bedrock. These agates are typically less colorful, with banded lines of grey and white chalcedony.[16] Greek agate is a name given to pale white to tan colored agate found in Sicily, once a Greek colony, back to[clarification needed] 400 BC. The Greeks used it for making jewelry and beads. Brazilian agate is found as sizable geodes of layered nodules. These occur in brownish tones inter-layered with white and gray. Quartz forms within these nodules, creating a striking specimen when cut opposite the layered growth axis. It is often dyed in various colors for ornamental purposes. Polyhedroid agate forms in a flat-sided shape similar to a polyhedron. When sliced, it often shows a characteristic layering of concentric polygons. It has been suggested that growth is not crystallographically controlled but is due to the filling-in of spaces between pre-existing crystals which have since dissolved.

Ulexite

Almost always white, and looks like a densely-packed bundle of white threads. It's opaque in one direction, and conducts light in the other. It's fiber-optic abilities gave it the nickname "T.V. rock". Family: Borate Formula: NaCaB5O6(OH)6·5H2O Color: Colorless to white Habit: Acicular to fibrous Crystal system: triclinic Streak: White Luster: vitreous; silky or satiny in fibrous aggregates Cleavage: ADD Fracture: Uneven Tenacity: Brittle Hardness: 2.5 SG: 1.95-1.96 Diaphaneity: Transparent to opaque Formation: Found in evaporite deposits and looks like a cotton ball tuft of acicular crystals. Found in CA and NV Other: Mined for the boron in it

Apophyllite

a specific group of phyllosilicates, a class of minerals. includes the members fluorapophyllite-(K), fluorapophyllite-(Na), hydroxyapophyllite-(K). derived from the Greek apophylliso, meaning "it flakes off", a reference to this class's tendency to flake apart when heated, due to water loss. Exfoliation of apophyllite is also possible by treating it with acids or simply by rubbing it. Family: Silicate Formula: (K,Na)Ca4Si8O20(F,OH)·8H2O Color: Usually white, colorless; also blue, green, brown, yellow, pink, violet Habit: Prismatic, tabular, massive Crystal system: P4/mnc (no. 128) Streak: white Luster: vitreous; pearly Cleavage: Fracture: uneven Tenacity: Hardness: 4.5 - 5 SG: 2.3 - 2.4 Diaphaneity: transparent to translucent Formation: typically found as secondary minerals in vesicles in basalt or other volcanic rocks. Other: Whereas most phyllosilicates have a T layer (silica backbone) consisting of interlocked 6-fold rings of silica tetrahedra, with pseudohexagonal symmetry, the T layer in apophyllite consists of interlocked 4-fold and 8-fold rings of silica tetrahedra with true tetragonal symmetry

Celestite

Also called celestine. The mineral is named for its occasional delicate blue color. Is one of the principal sources of the element strontium, commonly used in fireworks and in various metal alloys. Family: Sulfate Formula: SrSO4 Color: White, Pink, Pale green, Pale brown, Black, Pale blue, Reddish, Greyish; Colourless or lightly tinted in transmitted light Habit: Tabular to pyramidal crystals, also fibrous, lamellar, earthy, massive granular Crystal system: orthorhombic Streak: white Luster: vitreous, pearly on cleavages Cleavage: Fracture: uneven Tenacity: brittle Hardness: 3-3.5 SG: 3.95-3.97 Diaphaneity: transparent to translucent Formation: mostly found in sedimentary rocks, often associated with the minerals gypsum, anhydrite, and halite. In carbonate marine sediments, burial dissolution is a recognized mechanism of celestine precipitation. It is sometimes used as a gemstone. Celestine crystals are found in some geodes. Celestine geodes are understood to form by the replacement of alabaster nodules consisting of the calcium sulfates gypsum or anhydrite. Calcium sulfate is sparingly soluble, but strontium sulfate is mostly insoluble. Strontium-bearing solutions that come into contact with calcium sulfate nodules dissolve the calcium away, leaving a cavity. The strontium is immediately precipitated as celestine, with the crystals growing into the newly-formed cavity. Other: The world's largest known geode, a celestine geode 35 feet (11 m) in diameter at its widest point, is located near the village of Put-in-Bay, Ohio, on South Bass Island in Lake Erie.

Citrine

a transparent variety of quartz with a yellow to orange color. Its attractive color, high clarity, low price, and durability make it the most frequently purchased yellow to orange gem. Family: Silicate Formula: SiO2 Color: pale yellow to brown Habit: 6-sided prism ending in 6-sided pyramid (typical), drusy, fine-grained to microcrystalline, massive Crystal system: Streak: white Luster: vitreous Cleavage: Fracture: conchoidal Tenacity: Hardness: 7 SG: 2.65 Diaphaneity: translucent Formation: Color due to a submicroscopic distribution of colloidal ferric hydroxide impurities Other: Reddish orange and reddish brown are rare colors in quartz. Gems of these reddish colors are often called Madeira citrine. Citrine and topaz are both available in the yellow to orange color range, but citrine generally has a much lower cost. 1. citrine with a natural color2. citrine with a natural color, but enhanced by treatment3. citrine produced by heating light amethyst4. synthetic citrine (a man-made product)5. imitation citrine (a man-made product that is not SiO2)

Halite

Also known as "salt". Most is crushed and used in the winter on roads to control the accumulation of snow and ice. Significant amounts are also used by the chemical industry. An essential nutrient for humans and most animals, and it is also a favorite seasoning for many types of food. Family: Halide Formula: NaCl Color: Colorless or white when pure; impurities produce any color but usually yellow, gray, black, brown, red Habit: Predominantly cubes and in massive sedimentary beds, but also granular, fibrous and compact Crystal system: isometric/cubic Streak: White Luster: Vitreous Crystal Structure: Cleavage: perfect, cubic, three directions at right angles Fracture: conchoidal Tenacity: brittle Hardness: 2.5 SG: 2 Diaphaneity: transparent to translucent Formation: mainly a sedimentary mineral that usually forms in arid climates where ocean water evaporates. However, many inland lakes such as the Great Salt Lake of North America and the Dead Sea between Jordan and Israel are also locations where halite is forming today. Over geologic time, several enormous salt deposits have been formed when repeated episodes of seawater evaporation occurred in restricted basins. Some of these deposits are thousands of feet thick. When buried deeply they can erupt to form salt domes. Other:

Corundum

Defining mineral for 9 in MHS. Rock-forming mineral that is found in igneous, metamorphic, and sedimentary rocks. Hexagonal crystal structure. Extreme hardness and sometimes found as beautiful transparent crystals found in many different colors. Excellent abrasive and the different colors are ruby and sapphire. Family: Oxide Formula: Al2O3 Color: Typically gray to brown. Colorless when pure, but trace amounts of various metals produce almost any color. Chromium produces red (ruby) and combinations of iron and titanium produce blue (sapphire). Habit: Steep bipyramidal, tabular, prismatic, rhombohedral crystals, massive or granular Crystal system: Trigonal Streak: colorless, harder than streak plate. white Luster: adamantine to vitreous Crystal Structure: Cleavage: none Fracture: conchoidal to uneven Tenacity: Brittle Hardness: 9 defining mineral SG: 3.9-4.1 Diaphaneity: transparent to translucent Formation: Some of the world's most important ruby and sapphire deposits are found where the gems have weathered from basalt flows and are now found in the downslope soils and sediments. Corundum is also found in metamorphic rocks in locations where aluminous shales or bauxites have been exposed to contact metamorphism. Corundum's toughness, high hardness, and chemical resistance enable it to persist in sediments long after other minerals have been destroyed. This is why it is often found concentrated in alluvial deposits. Synthetic version produced using calcined bauxite and has more reliable properties suited for industrial properties. Other: Most people are familiar with corundum; however, very few people know it by its mineral name - instead they know it by the names "ruby" and "sapphire." A gemstone-quality specimen of corundum with a deep red color is known as a "ruby." A gemstone-quality corundum with a blue color is called a "sapphire." Colorless corundum is known as "white sapphire." Corundum of any other color is known as "fancy sapphire." High demand of rubys and sapphies leads to increase use of synthetic versions. In the mid-1800s, watch makers in Switzerland needed tiny bearings that were highly resistant to abrasion, used corundum called "jewel bearings". Synthetic ones eventually replace. Colorless synthetic sapphire is used for covering for the face of watches. Synthetic corundum is an essential part of many lasers. In fact, the first working laser was a "ruby laser," made by Theodore Maiman at Hughes Research Labs in 1960. chemically inert and resistant to heat. These properties make it a perfect material for making refractory products such as fire brick, kiln liners, and kiln furniture. Today, these products are usually made with synthetic corundum. Pure corundum is colorless, transparent, durable, and scratch resistant. Large crystals of clear synthetic corundum are grown, sawn into thin sheets, and then used as the windows of grocery store scanners, watch crystals, aircraft windows, and protective covers for electronic devices.

Actinolite

Derived from the Greek word aktis (ἀκτίς), meaning "beam" or "ray", because of the mineral's fibrous nature. intermediate member in a solid-solution series between magnesium-rich tremolite and iron rich ferro actinolite. Family: Silicate Formula: Ca2(Mg4.5-2.5Fe2+0.5-2.5)Si8O22(OH)2 Color: pale to dark green, yellowish green and black. White or grey when in asbestos Habit: bladed, fibrous, radial Crystal system: monoclinic Streak: white Luster: vitreous to dull Cleavage: perfect along one axis Fracture: uneven Tenacity: Hardness: 5-6 SG: 3 Diaphaneity: translucent to transparent Formation: commonly found in metamorphic rocks, such as contact aureoles surrounding cooled intrusive igneous rocks. It also occurs as a product of metamorphism of magnesium-rich limestones Other: Some forms of actinolite are used as gemstones. One is nephrite, one of the two types of jade

Diamond

Each carbon is surrounded by four other carbons ad connected by strong covalent bonds. The strongest known natural substance. Chemically resistant and has the highest thermal conductivity of any natural material. A high index of refraction, high dispersion, adamantine luster. World's most popular gemstone, used in specialty lenses requiring durability and performance. Family: Native Formula: C Color: most brown or yellow, jewelry favors colorless. those in hies of red, orange, green, blue, pink, purple, violet, and yellow are extremely rare. Habit: octahedral Crystal system: isometric Streak: none or colorless, harder than a streak plate, Luster: adamantine Crystal Structure: Cleavage: perfect octahedral cleavage in 4 directions Fracture: uneven Tenacity: Hardness: 10, hardest known mineral, hardest parallel to octahedral planes, softest parallel to its cubic planes SG: 3.4-3.6 Diaphaneity: transparent, translucent, opaque Formation: Form at high temperatures and pressures that occur in the earth's mantle about 100 miles beneath the surface. Most diamonds found near the surface were delivered there through deep source volcanic eruptions. pieces of Mantle rock is delivered to the surface without melting, these xenoliths may contain diamonds. The diamond formation is present primarily in the mantle beneath the stable interiors of continental plates. subduction zones can also contain tiny diamonds. Impact sites by asteroids can also lead to tiny diamonds due to the high temperature and pressure surrounding the impact. Some meteorites can also contain nanodiamonds due to high-speed collisions in space. can now be created in labs for commercial use. Other: Industrial diamonds used in cutting, grinding, drilling, and polishing procedures. When diamonds are fashioned into a gem, facet angles are planned to reflect a maximum amount of light from its internal surfaces. High dispersion lets diamonds separate white light into components. 4C's in assessing quality, color, cut, clarity, carat weight. fancy color ones are very rare. Industrial diamonds used for abrasives, small particles are embedded in saw blades, drill bits, and grinding wheels. May also be ground into a fine powder and made into a diamond paste that is used for very fine grinding or polishing. diamonds used to cut and polish other diamonds, none done by lasers. can also be used for diamonds windows, diamond speaker domes, heat sinks, low friction micro bearings, wear-resistant parts. Synthetic diamonds created b high temperature and pressure are HTHP diamonds. The chemical vapor deposition process is CVD diamonds.

Rhodochrosite

Family: Carbonate Formula: Manganese carbonate, but is frequently replaced (Mn,Fe,Mg,Ca)CO3 Color: Pink, red, yellow, gray, brown Habit: Crystal system: Hexagonal Streak: white Luster: vitreous to pearly Crystal Structure: Cleavage: perfect in three directions Fracture: transparent to translucent Tenacity: Hardness: 3.5-4 SG: 3.5-3.7 Diaphaneity: transparent to translucent Formation: usually in fractures and cavities of metamorphic and sedimentary rocks. Assocated with silver deposits. In metamorphic, found as a vein and fracture filling mineral where it precipitates from ascending hydrothermal solutions. Forms in layers.Some form in cavities in sedimentary and metamorphic room when descending solutions deliver a supply of dissolved materials. accumulates in laters and may from stalactites and stalagmites. Other: substitutions change the SG, hardness, and color. weak effervescence with cold dilute HCl, Very popular gemstone. Often slayed to show patterns, slabs used to cut cabochons.

Limonite

Family: Oxide Formula: Fe2O3 Color: Green Habit: Crystal system: Streak: Luster: Crystal Structure: Cleavage: Fracture: Tenacity: Hardness: SG: Diaphaneity: Formation: Other:

Almandine

Family: Silicate Formula: Color: Habit: Crystal system: Streak: Luster: Cleavage: Fracture: Tenacity: Hardness: SG: Diaphaneity: Formation: Other:

Augite

Family: Silicate Formula: Color: Habit: Crystal system: Streak: Luster: Cleavage: Fracture: Tenacity: Hardness: SG: Diaphaneity: Formation: Other:

Rhodonite

Family: Silicate Formula: Color: Habit: Crystal system: Streak: Luster: Cleavage: Fracture: Tenacity: Hardness: SG: Diaphaneity: Formation: Other:

Sodalite

Family: Silicate Formula: Color: Habit: Crystal system: Streak: Luster: Cleavage: Fracture: Tenacity: Hardness: SG: Diaphaneity: Formation: Other:

Spodumene

Family: Silicate Formula: Color: Habit: Crystal system: Streak: Luster: Cleavage: Fracture: Tenacity: Hardness: SG: Diaphaneity: Formation: Other:

Staurolite

Family: Silicate Formula: Color: Habit: Crystal system: Streak: Luster: Cleavage: Fracture: Tenacity: Hardness: SG: Diaphaneity: Formation: Other:

Stilbite

Family: Silicate Formula: Color: Habit: Crystal system: Streak: Luster: Cleavage: Fracture: Tenacity: Hardness: SG: Diaphaneity: Formation: Other:

Willemite

Family: Silicate Formula: Color: Habit: Crystal system: Streak: Luster: Cleavage: Fracture: Tenacity: Hardness: SG: Diaphaneity: Formation: Other:

Zircon

Family: Silicate Formula: Color: Habit: Crystal system: Streak: Luster: Cleavage: Fracture: Tenacity: Hardness: SG: Diaphaneity: Formation: Other:

Kyanite

Family: Silicate Formula: Al2SiO5 Color: Blue, white, gray, green, colorless Habit: bladed Crystal system: triclinic Streak: white, colorless Luster: vitreous, pearly Cleavage: Perfect in two directions, faces sometimes striated Fracture: Tenacity: Hardness: 4.5 -5 along the length, 6.5-7 along the width SG: 3.5-3.7 Diaphaneity: transparent to translucent Formation: Other: Kyanite is used to manufacture a wide range of products. An important use is in the manufacture of refractory products such as the bricks, mortars, and kiln furniture used in high-temperature furnaces. For foundries, the molds that are used for casting high-temperature metals are often made with kyanite. Kyanite is also in products used in the automotive and railroad industries where heat resistance is important. Mullite, a form of calcined kyanite, is used to make brake shoes and clutch facings. well suited for the manufacture of a high-refractory-strength porcelain - a porcelain that holds its strength at very high temperatures. A familiar use of this type of porcelain is the white porcelain insulator on a spark plug. Kyanite is also used in some of the more common forms of porcelain, such as those used to make dentures, sinks, and bathroom fixtures Kyanite's heat resistance and hardness make it an excellent material for use in the manufacture of grinding wheels and cutting wheels. It is not used as the primary abrasive; instead, it is used as part of the binding agent that holds the abrasive particles together in the shape of a wheel. Kyanite, unlike most other minerals, can expand significantly when heated.

Epidote

Family: Silicate Formula: Ca2(Al2,Fe)(SiO4)(Si2O7)O(OH) Color: Usually yellowish green to pistachio green, sometimes brownish green to black Habit: Crystal system: Streak: Colorless Luster: vitreous to resinous Cleavage: perfect in one direction, imperfect Fracture: Tenacity: Hardness: 6-7 SG: 3.3-3.5 Diaphaneity: transparent to translucent to nearly opaque Formation: commonly found in regionally metamorphosed rocks of low-to-moderate grade. In these rocks, epidote is often associated with amphiboles, feldspars, quartz, and chlorite. It occurs as replacements of mineral grains that have been altered by metamorphism. It is frequently found in veins that cut granite. It occurs as monoclinic crystals in pegmatites. It is also found in massive form and as monoclinic crystals in marbles and schists that were formed or altered through contact metamorphism. Other: an end member of a solid solution series with clinozoisite. In that series, the iron of epidote is gradually replaced by aluminum to the end member clinozoisite composition of Ca2Al3(SiO4)(Si2O7)O(OH). Clinozoisite is usually lighter in color than epidote because iron is what produces epidote's greenish to brownish color. Epidote is a rock-forming mineral. Many regionally metamorphosed rocks contain small amounts of epidote. Two rock types that contain significant amounts of epidote are epidosite and unakite. Locations where these rocks can be found are rare, but at those locations significant amounts of these rocks can be present. Epidosite is a metamorphic rock composed mainly of epidote with small amounts of quartz. It forms when basalts in sheeted dikes and ophiolites are transformed by hydrothermal activity or metasomatism. Unakite is a rock that forms from the metamorphism of granite. Less-resistant minerals in the granite are altered to epidote or replaced by epidote, with the orthoclase and quartz remaining. It is an interesting pink and green colored rock that was first discovered in the Unakas Mountains of North Carolina, from which its name was derived.

Tremolite

Family: Silicate Formula: Ca2(Mg5.0-4.5Fe2+0.0-0.5)Si8O22(OH)2 Color: White, gray, lavender to pink, light green, light yellow Habit: Elongated prismatic, or flattened crystals; also as fibrous, granular or columnar aggregates Crystal system: monoclinic Streak: white Luster: vitreous and silky Cleavage: 56 and 124 degrees Fracture: Tenacity: brittle Hardness: 5-6 SG: 2.99-3.03 Diaphaneity: transparent to translucent Formation: Tremolite is an indicator of metamorphic grade since at high temperatures it converts to diopside. Tremolite occurs as a result of contact metamorphism of calcium and magnesium rich siliceous sedimentary rocks and in greenschist facies metamorphic rocks derived from ultramafic or magnesium carbonate bearing rocks.Tremolite forms a series with actinolite and ferro-actinolite. Other: Pure magnesium tremolite is creamy white, but the color grades to dark green with increasing iron content. Nephrite, one of the two minerals of the gemstone jade, is a green variety of tremolite. fibrous form of tremolite is one of the six recognised types of asbestos. This material is toxic, and inhaling the fibers can lead to asbestosis, lung cancer and both pleural and peritoneal mesothelioma. Fibrous tremolite is sometimes found as a contaminant in vermiculite, chrysotile (itself a type of asbestos) and talc.

Satin Spar

Family: Sulfate, variety of gypsum Formula: CaSO4.2H2O Color: Habit: Crystal system: monoclinic Streak: Luster: Cleavage: Fracture: Tenacity: Hardness: SG: Diaphaneity: Formation: Other:

Selenite

Family: sulfate, variety of gypsum Formula: CaSO4.2H2O Color: Habit: Crystal system: Streak: Luster: Cleavage: Fracture: Tenacity: Hardness: SG: Diaphaneity: Formation: Other:

Gold

Highly prized for its color, rarity, resistance to tarnish. Most found in the form of the native metal. It occurs in a solid solution series with the native element silver (as electrum), naturally alloyed with other metals like copper and palladium and also as mineral inclusions such as within pyrite. Less commonly, it occurs in minerals as compounds, often with tellurium Family: Native Formula: Au Color: Golden, whitens when naturally alloys with silver Habit: arborescent Crystal system: Isometric Streak: Golden, Yellow Luster: metallic Crystal Structure: Cleavage: None Fracture: Tenacity: Hardness: 2.5-3 SG: 19.3 when pure Diaphaneity: opaque Formation: Hydrothermal veins deposited by ascending solutions, as disseminated particles through some sulfide deposits and in placer deposits. Other: Most is used in jewelry, some in coinage, and bullion. Gold is an electrical conductor used in computers, circuits, appliances, cell phones, etc. Dental work, gilding, and many other uses. Gold is insoluble in nitric acid, which dissolves silver and base metals, a property that has long been used to refine gold and to confirm the presence of gold in metallic substances

Talc

It can be crushed into a white powder that is widely known as "talcum powder." Family: Silicate Formula: Mg3Si4O10(OH)2, Small amounts of Al or Ti can substitute for Si; small amounts of Fe, Mn, and Al can substitute for Mg; and, very small amounts of Ca can substitute for Mg. Color: green, white, gray, brown, or colorless Habit: Crystal system: monoclinic Streak: white to pale green Luster: pearly Cleavage: perfect Fracture: Tenacity: Hardness: 1 SG: 2.7-2.8 Diaphaneity: translucent Formation: found in the metamorphic rocks of convergent plate boundaries. It forms from at least two processes. Most large talc deposits in the United States formed when heated waters carrying dissolved magnesium and silica reacted with dolomiticmarbles. A second process of talc formation occurred when heat and chemically active fluids altered rocks such as dunite and serpentinite into talc. Other: "talcum powder." This powder has the ability to absorb moisture, absorb oils, absorb odor, serve as a lubricant, and produce an astringent effect with human skin. These properties have made talcum powder an important ingredient in many baby powders, foot powders, first aid powders, and a variety of cosmetics. A form of talc known as "soapstone" is also widely known. This soft rock is easily carved and has been used to make ornamental and practical objects for thousands of years. It has been used to make sculptures, bowls, countertops, sinks, hearths, pipe bowls, and many other objects. Although talcum powder and soapstone are two of the more visible uses of talc, they account for a very small fraction of talc consumption. Its hidden uses are far more common. Talc's unique properties make it an important ingredient for making ceramics, paint, paper, roofing materials, plastics, rubber, insecticides, and many other products. Talc has perfect cleavage that follows planes between the weakly bonded sheets. These sheets are held together only by van der Waals bonds, which allows them to slip past one another easily. This characteristic is responsible for talc's extreme softness, its greasy, soapy feel, and its value as a high-temperature lubricant. open pit mine where the rock is drilled, blasted, and partially crushed in the mining operation. The highest grade ores are produced by selective mining and sorting operations. Partially crushed rock is taken from the mine to a mill, where it is further reduced in particle size. Impurities are sometimes removed by froth flotation or mechanical processing. The mills usually produce crushed or finely ground talc that meets customer requirements for particle size, brightness, composition, and other properties.

Kaolinite

It is an important industrial mineral. It is a layered silicate mineral, with one tetrahedral sheet of silica (SiO4) linked through oxygen atoms to one octahedral sheet of alumina (AlO6) octahedra.[7] Rocks that are rich in kaolinite are known as kaolin /ˈkeɪ.ə.lɪn/ or china clay.[8] Family: Silicate Formula: Al2(OH)4Si2O5 Color: White to cream, sometimes red, blue or brown tints from impurities and pale-yellow; also often stained various hues, tans and browns being common. Habit: Rarely as crystals, thin plates or stacked, More commonly as microscopic pseudohexagonal plates and clusters of plates, aggregated into compact, claylike masses Crystal system: triclinic Streak: white Luster: pearly to dull earthy Cleavage: Fracture: Tenacity: flexible but inelastic Hardness: 2-2.5 SG: 2.16-2.68 Diaphaneity: opaque Formation: 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 liquid slurry. Other: It is described as a 1:1 or TO clay mineral because its crystals consist of stacked TO layers. Each TO layer consists of a tetrahedral (T) sheet composed of silicon and oxygen ions bonded to an octahedral (O) sheet composed of oxygen, aluminum, and hydroxyl ions. The main use of the mineral kaolinite (about 50% of the time) is the production of paper; its use ensures the gloss on some grades of coated paper.[55] Kaolin is also known for its capabilities to induce and accelerate blood clotting. In April 2008 the US Naval Medical Research Institute announced the successful use of a kaolinite-derived aluminosilicate infusion in traditional gauze, known commercially as QuikClot Combat Gauze,[56] which is still the hemostat of choice for all branches of the US military.

Chalcopyrite

It occurs in most sulfide mineral deposits throughout the world and has been the most important ore of copper for thousands of years. Family: sulfide Formula: CuFeS2 Color: Brass yellow. Tarnishes to gray green, sometimes iridescent. Habit: Crystal system: tetragonal Streak: greenish black Luster: metallic Cleavage: poor Fracture: Tenacity: Hardness: 3.5-4 SG: 4.1-4.3 Diaphaneity: opaque Formation: primary, crystallizing from melts as accessory minerals in igneous rocks. Some forms by magmatic segregation and is in the stratified rocks of a magma chamber. Some occurs in pegmatite dikes and contact metamorphic rocks. Some is disseminated through schist and gneiss. Many volcanogenic massive sulfide deposits containing chalcopyrite are known. The most significant chalcopyrite deposits to be mined are hydrothermal in origin. In these, some chalcopyrite occurs in veins and some replaces country rock. Associated ore minerals include pyrite, sphalerite, bornite, galena, and chalcocite. Chalcopyrite serves as the copper source for many secondary mineral deposits. Copper is removed from chalcopyrite by weathering or solution, transported a short distance, then redeposited as secondary sulfide, oxide, or carbonate minerals. Many malachite, azurite, covellite, chalcocite, and cuprite deposits contain this secondary copper. Other: similar appearance to pyrite and gold. Distinguishing these minerals is easy. Gold is soft, has a yellow streak and has a much higher specific gravity. Chalcopyrite is brittle and has a greenish gray streak. Pyrite is hard enough that it cannot be scratched with a nail, but chalcopyrite is easily scratched with a nail. surface of chalcopyrite loses its metallic luster and brass-yellow color upon weathering. It tarnishes to a dull, gray-green color, but in the presence of acids the tarnish can develop a red to blue to purple iridescence. The iridescent colors of weathered chalcopyrite attract attention. Some souvenir shops sell chalcopyrite that has been treated with acid as "peacock ore."

Barite

It receives its name from the Greek word "barys" which means "heavy." High specific gravity of 4.5, which is exceptional for a nonmetallic mineral. Makes it suitable for a wide range of industrial, medical, and manufacturing uses. Also serves as the principal ore of barium. Family: Sulfate Formula: BaSO4 Color: Colorless, white, light blue, light yellow, light red, light green Habit: Crystal system: orthorhombic Streak: white Luster: vitreous to pearly Cleavage: very good, basal, prismatic Fracture: Tenacity: Hardness: 2.5 - 3.5 SG: 4.5 Diaphaneity: transparent to translucent Formation: often occurs as concretions and void-filling crystals in sediments and sedimentary rocks. It is especially common as concretions and vein fillings in limestone and dolostone. Where these carbonate rock units have been heavily weathered, large accumulations of barite are sometimes found at the soil-bedrock contact. Many of the commercial barite mines produce from these residual deposits. Barite is also found as concretions in sand and sandstone. These concretions grow as barite crystallizes within the interstitial spaces between sand grains. Sometimes crystals of barite grow into interesting shapes within the sand. These structures are known as "barite roses" (see photo). They can be up to several inches in length and incorporate large numbers of sand grains. Occasionally barite is so abundant in a sandstone that it serves as the "cement" for the rock. Barite is also a common mineral in hydrothermal veins and is a gangue mineral associated with sulfide ore veins. It is found in association with ores of antimony, cobalt, copper, lead, manganese, and silver. In a few locations barite is deposited as a sinter at hot springs Other: Most barite produced is used as a weighting agent in drilling muds. This is what 99% of the barite consumed in the United States is used for. These high-density muds are pumped down the drill stem, exit through the cutting bit and return to the surface between the drill stem and the wall of the well. This flow of fluid does two things: 1) it cools the drill bit; and, 2) the high-density barite mud suspends the rock cuttings produced by the drill and carries them up to the surface. Barite is also used as a pigment in paints and as a weighted filler for paper, cloth and rubber. The paper used to make some playing cards has barite packed between the paper fibers. This gives the paper a very high density that allows the cards to be "dealt" easily to players around a card table. Barite is used as a weighting filler in rubber to make "anti-sail" mudflaps for trucks. Barite is the primary ore of barium, which is used to make a wide variety of barium compounds. Some of these are used for x-ray shielding. Barite has the ability to block x-ray and gamma-ray emissions. Barite is used to make high-density concrete to block x-ray emissions in hospitals, power plants, and laboratories. Barite compounds are also used in diagnostic medical tests. If a patient drinks a small cup of liquid that contains a barium powder in a milkshake consistency, the liquid will coat the patient's esophagus. An x-ray of the throat taken immediately after the "barium swallow" will image the soft tissue of the esophagus (which is usually transparent to x-rays) because the barium is opaque to x-rays and blocks their passage. A "barium enema" can be used in a similar way to image the shape of the colon.

Zincite

Its blood-red colour and orange-yellow streak are characteristic, Family: Oxide Formula: ZnO Color: Orange, yellow-orange to deep red, red, rarely yellow, rarely green and colorless to white Habit: Disseminated - occurs in small, distinct particles dispersed in matrix. Crystal system: Hexagonal Streak: yellowish orange Luster: subadamantine to resinous Crystal Structure: Cleavage: Fracture: conchoidal Tenacity: brittle Hardness: 4 SG: 5.64-5.68 Diaphaneity: translucent, transparent in thin fragments Formation: usually found in platy or granular masses. Its blood-red colour and orange-yellow streak are characteristic, as is also its common association with black franklinite and white calcite. Notable specimens have been found at Franklin and Sterling Hill, near Ogdensburg, N.J. Other: Zincite crystals can be grown artificially, and synthetic zincite crystals are available as a by-product of zinc smelting. Synthetic crystals can be colorless or can range in color from dark red, orange, or yellow to light green. Synthetic zincite crystals Both natural and synthetic zincite crystals are significant for their early use as semiconductor crystal detectors in the early development of crystal radios before the advent of vacuum tubes. As an early radio detector it was used in conjunction with another mineral, galena, and this device was known as the cat's-whisker detector.

Pyrolusite

Its name is from the Greek for fire and to wash, in reference to its use as a way to remove tints from glass. Imporant ore of manganese. Stains to the touch. Usually found as matte-black powdery to fibrous crusts, sometimes in botryoidal aggregates or columnar, more rarely as druzes of small prismatic to tabular, dark grey metallic crystals. Family: Oxide Formula: MnO2 Color: Darkish, black to a lighter grey, sometimes bluish Habit: granular to massive, botryoidal, crystals rare. Crystal system: Tetragonal Streak: black to bluish black Luster: metallic, dull to earthy Crystal Structure: Cleavage: perfect on 110 Fracture: brittle Tenacity: Hardness: 6-6.5, 2 when massive SG: 4.4 - 5.06 Diaphaneity: opaque Formation: under oxidizing conditions in hydrothermal deposits. It also occurs in bogs and often results from alteration of manganite Other: Some of the most famous early cave paintings in Europe were made using this. Blocks are found often at Neanderthal sites. It may have been kept as a pigment for cave paintings, but it has also been suggested that it was powdered and mixed with tinder fungus for lighting fires. Manganese dioxide, in the form of umber, was one of the earliest natural substances used by human ancestors. It was used as a pigment at least from the middle paleolithic. It may have been also used by the Neanderthals in fire-making. The metal is obtained by reduction of the oxide with sodium, magnesium, aluminium, or by electrolysis. Pyrolusite is extensively used for the manufacture of spiegeleisen and ferromanganese and of various alloys such as manganese-bronze. As an oxidizing agent it is used in the preparation of chlorine; indeed, chlorine gas itself was first described by Karl Scheele in 1774 from the reaction products of pyrolusite and hydrochloric acid. Natural pyrolusite has been used in batteries, but high-quality batteries require synthetic products. Pyrolusite is also used to prepare disinfectants (permanganates) and for decolorizing glass. When mixed with molten glass it oxidizes the ferrous iron to ferric iron, and so discharges the green and brown tints (making it classically useful to glassmakers as a decolorizer). As a coloring material, it is used in calico printing and dyeing; for imparting violet, amber, and black colors to glass, pottery, and bricks; and in the manufacture of green and violet paints.

Milky Quartz

Milk quartz or milky quartz is the most common variety of crystalline quartz. The white color is caused by minute fluid inclusions of gas, liquid, or both, trapped during crystal formation,[ making it of little value for optical and quality gemstone applications Family: Silicate Formula: SiO2 Color: white Habit: Crystal system: Streak: colorless Luster: Cleavage: Fracture: Tenacity: Hardness: 7 SG: 2.6 Diaphaneity: Formation: Other:

Fluorite

Mineral used for hardness of 4 in Moh's hardness scale. It is a very common rock-forming mineral Family: Halide Formula: CaF2 Color: Typically purple, green, and yellow. Also colorless, blue, red, and black. Habit: Crystalline, disseminated, massive Crystal system: isometric Streak: white Luster: vitreous Crystal Structure: Cleavage: four directions perfect Fracture: Tenacity: Hardness: 4 SG: 3.2 Diaphaneity: transparent to translucent Formation: deposited in veins by hydrothermal processes. In these rocks it often occurs as a gangue mineral associated with metallic ores. Also found in the fractures and cavities of some limestones and dolomites. Other: In 1852, George Gabriel Stokes discovered the ability to produce a blue glow when illuminated with light, which in his words was "beyond the violet end of the spectrum." He called this phenomenon "fluorescence" Many do not fluorese. Fluorescence is thought to be caused when trace amounts of yttrium, europium, samarium, or other elements substitute for calcium. The primary uses are in the metallurgical, ceramics, and chemical industries; however, optical, lapidary, and other uses are also important. Fluorspar, the name used for fluorite when it is sold as a bulk material or in processed form, is sold in three different grades (acid, ceramic, and metallurgical). acid 9&%+, ceramic 85-96%, metallurgical 60-85%.

Magnetite

Most strongly magnetic mineral found in nature. Found in igneous, metamorphic, and sedimentary rocks. It is the most commonly mined ore of iron. It is also the mineral with the highest iron content (72.4%). Ferrimagnetic. reacts with oxygen to produce hematite. Family: Oxide Formula: Fe3O4 Color: Black to silvery gray Habit: octahedral Crystal system: isometric Streak: black Luster: metallic to submetallic Crystal Structure: Cleavage: none Fracture: Tenacity: Hardness: 6-6.5 SG: 5.2 Diaphaneity: opaque Formation: Hydrothermal synthesis usually produces single octahedral crystals.In the presence of mineralizers, magnetite grew as crystals whose shapes were a combination of rhombic-dodechahedra forms. Magnetite is sometimes found in large quantities in beach sand. Huge deposits have been found in banded iron formations. Other: Most of the iron ore mined today is a banded sedimentary rock known as taconite that contains a mixture of magnetite, hematite, and chert. Once considered a waste material, taconite became an important ore after higher grade deposits were depleted. Today's commercial taconites contain 25 to 30% iron by weight. At the mine site, the taconite ore is ground to a fine powder, and strong magnets are used to separate magnetically susceptible particles containing magnetite and hematite from the chert. The concentrate is then mixed with small amounts of limestone and clay, then rolled into small round pellets. These pellets are easy to handle and transport by ship, rail, or truck. They can be directly loaded into a blast furnace at a mill and be used to produce iron or steel. Normal magnetite is attracted to a magnet, but some specimens are automagnetized and have the ability to attract small pieces of iron, small pieces of magnetite, and other magnetic objects. This form of magnetite, known as "lodestone," was man's first encounter with the property of magnetism. Pieces of lodestone suspended on a string served as the first magnetic compasses and were used in China as early as 300 BC. Tiny crystals of magnetite are present in many rocks. In the crystallization of an igneous rock, tiny crystals of magnetite form in the melt, and because they are magnetic, they orient themselves with the direction and polarity of Earth's magnetic field. This preserves the orientation of Earth's magnetic field within the rock at the moment of crystallization. Today, geologists can study the magnetic properties of rocks of various age and reconstruct the history of change in Earth's magnetic field. This information is available for multiple locations on multiple continents. It can also be used to learn about plate tectonics and the movement of continents over time. A similar orientation of tiny magnetite grains occurs in the settling of sediment particles, locking clues to Earth's magnetic history into some sedimentary rocks. Due to its tendency to react with oxygen to form hematite and various iron oxyhydroxides (e.g., ferrihydrite, goethite), magnetite can be used as a powerful tool to explore oxygen concentrations in rocks during geological processes. Can be found in the brain but not much is understood about it.

Graphite

Naturally occurring form of crystalline carbon. found in metamorphic and igneous rocks. It is extremely soft, cleaves with very light pressure, and has a very low specific gravity. Extremely resistant to heat and nearly inert in contact with almost any other material. These extreme properties give it a wide range of uses in metallurgy and manufacturing Family: Native Formula: C Color: Steel gray to black Habit: tabular, 6 sided foliated masses, granular to compacted masses Crystal system: Hexagonal Streak: black Luster: metallic, sometimes submetallic or earthy Crystal Structure: Cleavage: perfect in one direction Fracture: flaky, rough when not on cleavage Tenacity: Flexible non elastic, sectile Hardness: 1-2 SG: 2.1 - 2.3 Diaphaneity: opaque Formation: forms when carbon is subjected to heat and pressure in the crust and upper mantle. Pressures in the range of 75 pounds/in^2 and temperatures in the range of 750C. Most at the surface formed at convergent plate boundaries where organic-rich shales and limestones were subjected to the heat and pressure of regional metamorphism. Some forms from the metamorphism of coal seams, when mined is amorphous graphite. small amount forms by the reaction of carbon compounds in the rock during hydrothermal metamorphism can be mobilized ad deposited in veins, has a high degree of crystallinity preferred material for electrical uses. Synthetic graphite is made by heating high carbon materials like petroleum coke and coal-tar pitch to temperatures in the range of 2500 to 3000C. Other: Carbon atoms are linked in a hexagonal network which forms sheets that are one atom thick. poorly connected and easily cleave or slide over one another. individual layers are called graphene. atoms in each plane are bonded covalently with only 3/4 of the bonding sites satisfied, fourth electron free to migrate in the plane, electrically conductive. Used to manufacture heat and chemical resistant containers and other objects. Battery anodes. A dry lubricant. The "lead" in pencils.

Malachite

One of the first ores used to produce copper metal but it has lost prominence in this respect. Also has been used as a gemstone and sculptural material. Easy to grind into powder and therefore used for pigment and coloring ages for thousands of years. Family: Carbonate Formula: Cu2(CO3)(OH)2 Color: Green Habit: massive, botryoidal, fibrous, or stalagmitic, individual crystals are rare, but occur as tabular or acicular Crystal system: Monoclinic Streak: light green Luster: crystals are adamantine to vitreous, silky if fibrous, dull to earthy if massive, polishes to a very bright luster Crystal Structure: Cleavage: perfect in one direction, fair in a second Fracture: subconchoidal to uneven Tenacity: Hardness: 3.5-4 SG: 3.6-4 Diaphaneity: most are opaque, crystals are translucent Formation: shallow depths within the earth, oxidizing zone above copper deposits. precipitates from descending solutions in fractures, caverns, and cavities, and the intergranuglar spaces of porous rock. Often forms within limestone. Other: bubbles or evervesces in contact with cold dilute HCl, when cut into slavs and pieces, san surfaces often exhibit banding and eyes

Topaz

One of the worlds favorite colored gemstones, mineral for number 8 on MHS, hardest silicate mineral Family: Silicate Formula: Al2SiO4(F,OH)2 Color: Natural colors include: colorless, yellow, orange, brown, red, pink, blue, green. Occurs in a wide range of treated colors, most often blue. Habit: Crystal system: orthorhombicc Streak: colorless Luster: vitreous Cleavage: perfect basal cleavage Fracture: Tenacity: Hardness: 8 SG: 3.4-3.6 Diaphaneity: translucne to transparent Formation: The fluorine in its composition is a limiting factor on its formation. Fluorine gas in concentrations high enough to form minerals only occurs in a few geologic environments. Most topaz grows as crystals within the veins and voids of igneous rocks. This topaz is found in the cavities of a pegmatite, or in the vesicles and intergranular spaces of rhyolite. These topaz crystals grow during the late stages of magma cooling and while degassing releases the fluorine necessary for topaz crystal growth. Precipitating in cavities, topaz sometimes develops nicely formed crystals. These crystals can have excellent clarity and can be used as a gem material. Many mineral collectors enjoy collecting gem-quality topaz crystals because they have the value of an excellent mineral specimen plus the value of a gem material. Topaz is also found as water-worn pebbles in stream sediments derived from the weathering of pegmatites and rhyolites. These are often produced by placer mining. Other: When allowed to grow in an unrestricted cavity, topaz forms orthorhombic crystals, often with striations that parallel the long axis of the crystal. It also has a distinct basal cleavage that breaks to form vitreous fracture surfaces perpendicular to the long axis of the crystal. This cleavage makes topaz a more fragile gemstone than its hardness of 8 would imply. Topaz is very hard, but it is also brittle and cleaves easily. most natural topaz is colorless. The most highly regarded colors are the reds and pinks, which receive their color from trace amounts of chromium. Chromium is also responsible for the color in violet and purple topaz. A variety known as "imperial topaz" is especially valuable because people enjoy its reddish orange to orangy red colors, which often both occur in the same crystal. Most of the world's imperial topaz is found in Brazil. Topaz with a natural blue color is very rare and valuable. Yellow, brown, and colorless topaz have lower values. These colors are often heated, irradiated, coated, and treated in other ways to alter their color. used for yellowish gemstones for at least two thousand years. At that time yellowish gems were called "topaz" Today most topaz offered in department stores and mall jewelry stores at low to moderate prices has been treated in a laboratory. Colorless topaz can be heated, irradiated, and coated with thin layers of metallic oxides to alter its color. Natural blue topaz is extremely rare and is usually pale blue. Almost all of the blue topaz offered in stores today is colorless topaz that has been irradiated and then heated to produce a blue color. "Swiss blue" and "London blue" are trade names for two of the most common varieties of treated blue topaz seen in today's market. Natural pink to purple topaz is also extremely rare, but these colors can be produced in a laboratory as well. The starting point is a stone cut from colorless topaz. It is first heated and then coated with a layer of metallic oxide to produce the pink color. If coated stones are worn in jewelry, over time the coating can wear thin or wear through at points on the stone where abrasion occurs. Some topaz is coated with a metallic oxide that gives the stone a multicolored iridescent luster. These stones, known as "mystic topaz," appear to change color if the observer moves the stone under a light or changes the angle of observation. These coatings are also thin and can be worn through during normal wear The type of irradiation used to transform colorless topaz into blue topaz can cause the irradiated material to become slightly radioactive. Fortunately, the radioactivity level of the topaz begins to decline as soon as treatment is complete. It eventually declines to a level that is safe for the topaz to be handled during manufacturing and be sold to the public in jewelry..

Vanadinite

an important ore of vanadium and a minor source of lead. Family: phosphate Formula: Pb5(VO4)3Cl Color: Usually bright yellow, orange, red or brown. Sometimes gray, black or colorless. Habit: Crystal system: Hexagonal Streak: pale yellow to yellowish-brown Luster: resinous to adamantine Cleavage: none Fracture: uneven or conchoidal Tenacity: brittle Hardness: 3-4 SG: 6.6-7.2 depending on purity Diaphaneity: opaque to translucent to transparent Formation: almost always a secondary mineral that forms in the oxidized zone above lead deposits. It is often found in oxidized veins containing primary and secondary minerals of lead. It is commonly associated with the oxidation of galena. The vanadium and chlorine are usually leached from the overburden by downward-moving waters. Vanadinite deposits are usually found in arid regions, with notable deposits in Argentina, Australia, Morocco, Namibia, and the southwestern United States. Other: Although the ideal composition for vanadinite is Pb5(VO4)3Cl, phosphorus and arsenic often substitute for vanadium in the mineral's crystal lattice. This results in a wide range of compositions which influence the specific gravity, color, and other properties. A solid solution series exists between vanadinite and and mimetite Pb5(AsO4)3Cl. Small amounts of calcium, zinc and copper can substitute for lead. Vanadinite, along with carnotite and roscoelite, are important ores of vanadium metal. Vanadinite is also a minor ore of lead. Both vanadium and lead are produced wherever vanadinite is mined. Vanadinite is very popular as a specimen with mineral collectors. They enjoy its bright colors, showy hexagonal crystals, resinous color, and adamantine luster.

Smoky Quartz

color-variety of crystalline quartz. It ranges from a light yellowish brown to a brown that is so dark that it appears to be black. Less-desirable specimens have a grayish brown color. When cut as a gem, stones with an orangish brown to a reddish brown color are preferred by many people. Family: Silicate Formula: SiO2 Color: Light yellowish brown to orangish brown to reddish brown to brown so dark that it appears to be black. Many specimens are grayish. Often zoned. Habit: Crystal system: hexagonal Streak: colorless Luster: vitreous Cleavage: none Fracture: conchoidal Tenacity: Hardness: 7 SG: 2.6-2.7 Diaphaneity: transparent to translucent Formation: The color of smoky quartz is produced when natural radiation, emitted from the surrounding rock, activates color centers around aluminum impurities within the crystalline quartz. mainly found in quartz veins and pegmatite dikes that cut across igneous and metamorphic rocks. Well-formed crystals are often found in cavities of igneous and metamorphic rocks along the margins of a pegmatite. Smoky quartz formed at lower temperatures is sometimes found in fractures of sedimentary and metamorphic rocks with no known igneous association. Radioactive mineral deposits in many parts of the world are associated with very dark smoky quartz. The very dark quartz at these locations was probably colored by emissions from the radioactive minerals. Other:

Chalcedony

composed of very fine intergrowths of quartz and moganite. These are both silica minerals, but they differ in that quartz has a trigonal crystal structure, while moganite is monoclinic. Family: Silicate Formula: SiO2 Color: commonly white to gray, grayish-blue or a shade of brown ranging from pale to nearly black Habit: Crystal system: trigonal or monoclinic Streak: white Luster: waxy, vitreous, dull, greasy, silky Cleavage: none Fracture: uneven, splintery, conchoidal Tenacity: Hardness: 6-7 SG: 2.59-2.61 Diaphaneity: translucent Formation: Other: Chalcedony was used in tool making as early as 32,000 BP in Central Australia. In the Bronze Age chalcedony was in use in the Mediterranean region. Hot wax would not stick to it so it was often used to make seal impressions. Chalcedony is more soluble than quartz under low-temperature conditions, despite the two minerals being chemically identical. This is thought to be because chalcedony is extremely finely grained (cryptocrystalline), and so has a very high surface area to volume ratio. It has also been suggested that the higher solubility is due to the moganite component.

Basalt

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. Basalt underlies more of Earth's surface than any other rock type. Most areas within Earth's ocean basins are underlain by basalt. Although basalt is much less common on continents, lava flows and flood basalts underlie several percent of Earth's land surface. Basalt is a very important rock. also an abundant rock on the Moon. Type: Composition: 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. 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 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. a mantle plume or hotspot delivers enormous amounts of basaltic lava through the continental crust and up to Earth's surface. These eruptions can be from either vents or fissures. They have produced the largest basalt flows on the continents. The eruptions can occur repeatedly over millions of years, producing layer after layer of basalt stacked in a vertical sequence Other: Olympus Mons is a shield volcano on Mars. It, like most other volcanic features on Mars, was formed from basaltic lava flows. It is the highest mountain on Mars and is the largest known volcano in our solar system. 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.

Andesite

fine-grained, extrusive igneous rocks that are usually light to dark gray in color. They have a mineral composition that is intermediate between granite and basalt. Andesite is a rock typically found in volcanoes above convergent plate boundaries between continental and oceanic plates. Type: Igneous Composition: often weathers to various shades of brown. In the field, weathered specimens must be broken to properly see their color and their mineral composition. Classroom specimens usually do not require breakage. Andesite is rich in plagioclase feldspar and amphibole minerals. Quartz and pyroxene minerals may be absent or present in small quantities. Small amounts of mica will be present as biotite or muscovite. Andesite usually does not contain olivine. The accompanying chart titled "Generalized Composition Ranges of Common Igneous Rocks" illustrates the mineral composition of andesite. Formation: typically found in lava flows produced by stratovolcanoes above subduction zones. 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 clearly without the use of a hand lens or other 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. Other: Occasionally, andesites contain large, visible grains of plagioclase, amphibole, or pyroxene. These large crystals are known as "phenocrysts." They begin forming when a magma, which is cooling at depth, approaches the crystallization temperature of some of its minerals. These high-crystallization-temperature minerals begin forming below the surface and grow to visible sizes before the magma erupts. When the magma erupts onto the Earth's surface, the rest of the melt crystallizes quickly. This produces a rock with two different crystal sizes: large crystals that formed slowly at depth (the "phenocrysts"), and small crystals that formed quickly at the surface (known as "groundmass"). "Andesite porphyry" is the name used for these rocks with two crystal sizes. The name of an abundant phenocryst mineral may be used as an adjective to the rock name. An example is the hornblende andesite porphyry shown in the accompanying photo.

Rutile

found in igneous, metamorphic and sedimentary rocks throughout the world. Also occurs as needle-shaped crystals in other minerals. Used as an ore of titanium, it is crushed into a white powder that is used as a pigment in paints, and it is processed for use in a multitude of products. Manufacturing titanium oxide pigments, manufacturing refractory ceramics, and production of titanium metal. Networks of needle-shaped rutile crystals produce the "eyes" and "stars" in many gems, such as star ruby and star sapphire. Family: Oxide Formula: TiO2 Color: Red to reddish brown, black, yellow to gold Habit: Crystal system: tetragonal Streak: Red to brown Luster: Adamantine to submetallic Crystal Structure: Cleavage: Good Fracture: Tenacity: Hardness: 6-6.5 SG: 4.2-4.4 Diaphaneity: opaque, transparent on thin edges Formation: high specific gravity and is often concentrated by stream and wave action in "heavy mineral sands" that exist today in both onshore and offshore deposits. Much of the world's rutile production is mined from these sands. occurs as an accessory mineral in plutonic igneous rocks such as granite and in deep-source igneous rocks such as peridotite and lamproite. In metamorphic rocks, rutile is a common accessory mineral in gneiss, schist and eclogite. Well-formed crystals of rutile are sometimes found in pegmatite and skarn. Rutile and a number of other metallic ore minerals are mined together from sedimentary deposits known as "heavy mineral sands". These sediments are derived from the weathering of igneous and metamorphic rocks that contain abundant tiny grains of high-specific-gravity minerals such as rutile, ilmenite, anatase, brookite, leucoxene, perovskite, and titanite (also known as sphene). As these rocks weather, their more resistant mineral particles are washed into the marine coastal environment where they are sorted and concentrated according to their density by wave and current action. Where conditions are right and heavy minerals are abundant, these sediments can become minable deposits. Other: affinity for growing as prism-shaped crystals within other minerals. Long prisms of rutile occur in many different gem minerals. Quartz, corundum (ruby and sapphire), garnet, and andalusite are some of the more familiar. Sometimes these needles are coarse and clearly visible within the gem, as in many specimens of rutilated quartz. These needles produce attractive and interesting novelty gems when they have a pleasing color and arrangement. Titanium oxide pigments are used to produce white color in plastics, and they are used to make high-brightness paper. Titanium oxide gives these products a color that is resistant to fading. Titanium oxide is also nontoxic and chemically stable. Those properties allow it to be used as a pigment in food, cosmetics, pharmaceuticals, and many consumer products such as toothpaste.

Horneblende

group of dark-colored amphibole minerals found in many types of igneous and metamorphic rocks. These minerals vary in chemical composition but are all double-chain inosilicates with very similar physical properties. a rock-forming mineral that is an important constituent in acidic and intermediate igneous rocks such as granite, diorite, syenite, andesite, and rhyolite. It is also found in metamorphic rocks such as gneiss and schist. Family: Silicate Formula: (Ca,Na)2-3(Mg,Fe,Al)5(Si,Al)8O22(OH,F)2 Color: Usually black, dark green, dark brown Habit: Crystal system: monoclinic Streak: white, colorless Luster: vitreous Cleavage: 2 directions intersecting at 124 and 56 degress Fracture: Tenacity: brittle Hardness: 5-6 SG: 2.9-3.5 Diaphaneity: Formation: Other: dark color (usually black) and two directions of excellent cleavage that intersect at 124 and 56 degrees. The angle between the cleavage planes and hornblende's elongate habit can be used to distinguish it from augite and other pyroxene minerals that have a short blocky habit and cleavage angles intersecting at about 90 degrees. The presence of cleavage can be used to distinguish it from black tourmaline that often occurs in the same rocks. primary use might be as a mineral specimen. However, hornblende is the most abundant mineral in a rock known as amphibolite which has a large number of uses. It is crushed and used for highway construction and as railroad ballast. It is cut for use as dimension stone. The highest quality pieces are cut, polished, and sold under the name "black granite" for use as building facing, floor tiles, countertops, and other architectural uses. Hornblende has been used to estimate the depth of crystallization of plutonic rocks. Those with low aluminum content are associated with shallow depths of crystallization, while those with higher aluminum content are associated with greater depths of crystallization. This information is useful in understanding the crystallization of magma and also useful for mineral exploration.

Apatite Group

group of phosphate minerals with similar chemical compositions and physical properties. They are an important constituent of phosphorite, a rock mined for its phosphorus content and used to make fertilizers, acids, and chemicals. Relatively consistent hardness and serves as the index mineral for a hardness of five in the Mohs Hardness Scale. Specimens with excellent clarity and color are sometimes cut as faceted gemstones. Those with good color and translucence are cut as cabochons. Family: Phosphate Formula: a group of calcium phosphates Color: Green, brown, blue, yellow, violet, pink, colorless. Transparent specimens with excellent clarity and vivid color are used as gemstones. Habit: Crystal system: hexagonal Streak: white Luster: vitreous to subresionous Crystal Structure: Cleavage: poor to indistinct Fracture: Tenacity: Hardness: 5 SG: 3.1-3.3 Diaphaneity: transparent to translucnet Formation: Apatite forms under a wide variety of conditions and is found in igneous, metamorphic, and sedimentary rocks. The most important deposits of apatite are in sedimentary rocks formed in marine and lacustrine environments. There, phosphatic organic debris (such as bones, teeth, scales, and fecal material) had accumulated and was mineralized during diagenesis. Some of these deposits contain enough phosphorus that they can be mined and used to produce fertilizers and chemical products. Apatite occasionally occurs as well-formed hexagonal crystals in hydrothermal veins and pegmatite pockets. These crystals often have a very high clarity and a vivid color and have been cut into gems for collectors. Other: Phosphate rock and phosphorite are names used for sedimentary rocks that contain at least 15% to 20% phosphate on the basis of weight. The phosphorous content in these rocks is mainly derived from the presence of apatite minerals. Determining which apatite-group minerals are contained in the rock cannot be determined without laboratory testing because their particle sizes are so small. Most phosphate rock has a non-detrital origin similar to limestone. Some of the phosphate is deposited by precipitation from solution; some is the remains and waste products of organisms; and, some is deposited by groundwater during diagenesis. Like limestone, phosphate rock is deposited in sedimentary basins where the influx of detrital material is relatively low. That allows the phosphate to accumulate with very little dilution from other materials. Where the dilution rate is high, phosphatic shales, mudstones, limestones, and sandstones will form instead of phosphate rock. Most of the phosphate rock mined throughout the world is used to produce phosphate fertilizer. It is also used to produce animal feed supplements, phosphoric acid, elemental phosphorous, and phosphate compounds for the chemical industry.

Olivine

group of rock-forming minerals that are typically found in mafic and ultramafic igneous rocks such as basalt, gabbro, dunite, diabase, and peridotite. They are usually green in color. a very popular green gemstone known as peridot. Family: Silicate Formula: Typically (Mg, Fe)2SiO4. Ca, Mn, and Ni rarely occupy the Mg and Fe positions. Color: Usually olive green, but can be yellow-green to bright green; iron-rich specimens are brownish green to brown Habit: Crystal system: Streak: colorless Luster: vitreous Cleavage:poor. brittle with a conchoidal fracture Fracture: Tenacity: Hardness: 6.5-7 SG: 3.2-4.4 Diaphaneity: transparent to translucent Formation: Most olivine found at Earth's surface is in dark-colored igneous rocks. It usually crystallizes in the presence of plagioclase and pyroxene to form gabbro or basalt. These types of rocks are most common at divergent plate boundaries and at hot spots within the centers of tectonic plates. Olivine has a very high crystallization temperature compared to other minerals. That makes it one of the first minerals to crystallize from a magma. During the slow cooling of a magma, crystals of olivine may form and then settle to the bottom of the magma chamber because of their relatively high density. This concentrated accumulation of olivine can result in the formation of olivine-rich rocks such as dunite in the lower parts of a magma chamber. Crystals of olivine are sometimes formed during the metamorphism of a dolomitic limestone or dolomite. The dolomite contributes magnesium, and silica is obtained from quartz and other impurities in the limestone. When olivine is metamorphosed, it is transformed into serpentine. Olivine is one of the first minerals to be altered by weathering. Because it is so easily altered by weathering, olivine is not a common mineral in sedimentary rocks and is only an abundant constituent of sand or sediment when the deposit is very close to the source. Other: an important mineral in Earth's mantle. Its presence as a mantle mineral has been inferred by a change in the behavior of seismic waves as they cross the Moho - the boundary between Earth's crust and mantle. The presence of olivine in Earth's interior is also confirmed by the presence of olivine in xenoliths, which are thought to be pieces of the upper mantle delivered to Earth's surface in the magmas of deep-source volcanic eruptions. Olivine is also an abundant mineral in the lower portion of many ophiolites. These are slabs of oceanic crust (with part of the upper mantle attached) that have been thrust up onto an island or a continent. identified in a large number of stony and stony-iron meteorites. Most olivine is used in metallurgical processes as a slag conditioner. High-magnesium olivine (forsterite) is added to blast furnaces to remove impurities from steel and to form a slag. Olivine has also been used as a refractory material. It is used to make refractory brick and used as a casting sand. Both of these uses are in decline as alternative materials are less expensive and easier to obtain. The chemical composition of most olivine falls somewhere between pure forsterite (Mg2SiO4) and pure fayalite (Fe2SiO4). In that series, Mg and Fe can substitute freely for one another in the mineral's atomic structure - in any ratio. This type of continuous compositional variation is known as a "solid solution" and is represented in a chemical formula as (Mg,Fe)2SiO4. The name "olivine" is used instead of "forsterite" or "fayalite" because a chemical analysis or other detailed testing is needed to determine which one is dominant - if either is dominant. The name "olivine" serves as a quick, convenient, and inexpensive way to put a name on the material. A list of the more common olivine minerals and their composition is given in the table below. Forsterite used for peridot.

Opal

hydrated amorphous form of silica. classed as a mineraloid. two broad classes of: precious and common. Precious displays play-of-color (iridescence), common does not Family: Silicate Formula: SiO2.nH2OIt is amorphous, without a crystalline structure, and without a definite chemical composition (it contains a variable amount of water, as shown by the "n" in its chemical composition). Therefore opal is a "mineraloid" rather than a "mineral." Color: Commonly having a bodycolor of white, yellow, gray, black, or brown; however, the bodycolor of opal can be any color. Some of the most beautiful common opals are red, orange, pink, green,or blue. The play-of-color of precious opal displays spectral colors of red, orange, yellow, green, blue, and viole Habit: Irregular veins, in masses, in nodules Crystal system: amorphous Streak: white Luster: Rough opal can have a dull, pearly, waxy, or vitreous luster. Most opal polishes to a vitreous luster. Cleavage: none Fracture: conchoidal Tenacity: Hardness: 5-6 SG: 2-2.2 Diaphaneity: translucent, opaque Formation: It is deposited at a relatively low temperature and may occur in the fissures of almost any kind of rock, being most commonly found with limonite, sandstone, rhyolite, marl, and basalt. Other: Some opal also has an internal structure that consists of regularly packed spheres, which enables it to behave like a diffraction grating and separate light into its component colors - similar to what is done by a prism. This phenomenon is known as "play-of-color". Together, these properties enable it to be a gemstone, albeit a fragile one.

Microcline

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. Microcline forms during slow cooling of orthoclase; it is more stable at lower temperatures than orthoclase. Family: Silicate Formula: KAlSi3O8 Color: pink Habit: Can be anhedral or euhedral. Grains are commonly elongate with a tabular appearance. May contain lamellae which formed from exsolved albite. Crystal system: triclinic Streak: white Luster: vitreous Cleavage: Fracture: Tenacity: brittle Hardness: 6-6.5 SG: 2.5-2.6 Diaphaneity: transaprent to translucnet Formation: Other: generally characterized by cross-hatch twinning that forms as a result of the transformation of monoclinic orthoclase into triclinic microcline. Microcline 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 "microcline" Microcline is identical to orthoclase in many physical properties, and can be distinguished by x-ray or optical examination. When viewed under a polarizing microscope, microcline exhibits a minute multiple twinning which forms a grating-like structure that is unmistakable. Amazon stone, or amazonite, is a green variety of microcline. The chemical compound name is potassium aluminium silicate, and it is known as E number reference E555. It was the subject in 2018 of a Call for technical and toxicological data from the EFSA. In 2008, it (along with other Aluminum compounds) was the subject of a Scientific Opinion of the Panel on Food Additives, Flavourings, Processing Aids and Food Contact Materials from the EFSA.

Jasper

impure variety of silica, usually red, yellow, brown or green in color; and rarely blue. The common red color is due to iron(III) inclusions Family: Silicate Formula: SiO2 Color: Most commonly red, but may be yellow, brown, green or (rarely) blue Habit: Crystal system: hexagonal Streak: Luster: vitreous Cleavage: indiscernable Fracture: Tenacity: Hardness: 6.5-7 SG: 2.5-2.9 Diaphaneity: opaque Formation: Patterns arise during the consolidation process forming flow and depositional patterns in the original silica-rich sediment or volcanic ash. Hydrothermal circulation is generally thought to be required in the formation of jasper. Other: breaks with a smooth surface and is used for ornamentation or as a gemstone. It can be highly polished and is used for items such as vases, seals, and snuff boxes. main component in the silica-rich parts of banded iron formations (BIFs) which indicate low, but present, amounts of dissolved oxygen in the water such as during the Great Oxidation Event or snowball earths

Labradorite

is a feldspar mineral first identified in Labrador, Canada, which can display an iridescent effect. Labradorite is an intermediate to calcic member of the plagioclase series. It has an anorthite percentage (%An) of between 50 and 70. twinning is common. As with all plagioclase members, the crystal system is triclinic, and three directions of cleavage are present, two of which are nearly at right angles and are more obvious, being of good to perfect quality Family: Silicate Formula: Ca,Na)(Al,Si)4O8, where Ca/(Ca + Na) (% anorthite) is 50-70% Color: Gray, gray-white, brown, greenish, pale green, blue, yellow, colorless Habit: Crystals typically thin and tabular, rhombic in cross section, striated; massive Crystal system: Triclinic Streak: white Luster: vitreous to pearly on cleavages Cleavage: Fracture: uneven to conchoidal Tenacity: Hardness: 6-6.5 SG: 2.68-2.72 Diaphaneity: translucent to transparent Formation: occurs in mafic igneous rocks and is the feldspar variety most common in basalt and gabbro. The uncommon anorthosite bodies are composed almost entirely of labradorite.[4] It also is found in metamorphic amphibolites and as a detrital component of some sediments. Other: Labradorite can display an iridescent optical effect (or schiller) known as labradorescence peculiar reflection of the light from submicroscopical planes orientated in one direction (rarely in two directions); these planes have never such a position that they can be expressed by simple indices, and they are not directly visible under the microscope. Labradorescence is not a display of colors reflected from the surface of a specimen. Instead, light enters the stone, strikes a twinning surface within the stone, and reflects from it. The color seen by the observer is the color of light reflected from that twinning surface. Different twinning surfaces within the stone reflect different colors of light. Light reflecting from different twinning surfaces in various parts of the stone can give the stone a multi-colored appearance.

Stibnite

most important source for the metalloid antimony. Family: Sulfide Formula: Sb2S3 Color: Stibnite is grey when fresh, but can turn superficially black due to oxidation in air. Habit: Massive, radiating and elongated crystals. Massive and granular Crystal system: orthorhombic Streak: similar to color Luster: splendent on fresh crystal surfaces, otherwise metallic Cleavage: Fracture: subchonchoidal Tenacity: highly flexible but not elastic Hardness: 2 SG: 4.63 Diaphaneity: opaque Formation: occurs in hydrothermal deposits. Small deposits of stibnite are common, but large deposits are rare Other: Pastes of Sb2S3 powder in fat or in other materials have been used since ca. 3000 BC as eye cosmetics in the Mediterranean and farther afield; in this use, Sb2S3 is called kohl. finds use in pyrotechnic compositions, namely in the glitter and fountain mixtures. Needle-like crystals, "Chinese Needle", are used in glitter compositions and white pyrotechnic stars. The "Dark Pyro" version is used in flash powders to increase their sensitivity and sharpen their report. It is also a component of modern safety matches. It was formerly used in flash compositions, but its use was abandoned due to toxicity and sensitivity to static electricity

Calcite

most stable polymorph of calcium carbonate, is 3 on Moh's hardness scale Family: carbonate Formula: CaCO3 Color: Colorless or white, may have some shades of other colors Habit: Crystalline, granular, stalactitic, concretionary, massive, rhombohedral Crystal system: Trigonal Streak: white Luster: vitreous to pearly on cleavage surfaces Cleavage: Fracture: conchoidal Tenacity: brittle Hardness: 3 SG: 2.71 Diaphaneity: transparent to transulcent Formation: several pathways, from the classical terrace ledge kink model, crystallization of poorly ordered precursor phases (amorphous calcium carbonate, ACC) via an Ostwald ripening process, or the agglomeration of nanocrystals. the chemical precipitation of calcium carbonate and the transformation of shell, coral, fecal and algal debris into calcite during diagenesis. Other: a common constituent of sedimentary rocks, limestone in particular. Often the primary constituent of the shells of marine organisms. the hard parts of red algae, some sponges, brachiopods, echinoderms, some serpulids, most bryozoa, and parts of the shells of some bivalves, also trilobite eyes.

Biotite

name used for a large group of black mica minerals that are commonly found in igneous and metamorphic rocks. micas vary in chemical composition but are all sheet silicate minerals with very similar physical properties. Family: Silicate Formula: K(Mg,Fe)3(AlSi3O10)(F,OH)2 Color: black, dark green, dark brown Habit: Crystal system: monoclinic Streak: white to gray, flakes often produced Luster: vitreous on cleavage faces Cleavage: basal, perfect Fracture: Tenacity: Hardness: 2.5-3 SG: 2.7-3.4 Diaphaneity: thin sheets are transparent to translucent, books are opaque Formation: Other: It is a black mica with perfect cleavage and a vitreous luster on the cleavage faces. When biotite is separated into thin sheets, the sheets are flexible but will break upon severe bending. When held up to the light, the sheets are transparent to translucent with a brown, gray, or greenish color. Biotite has a small number of commercial uses. Ground mica is used as a filler and extender in paints, as an additive to drilling muds, as an inert filler and mold-release agent in rubber products, and as a non-stick surface coating on asphalt shingles and rolled roofing. It is also used in the potassium-argon and argon-argon methods of dating igneous rocks. Biotite and the brown mica known as phlogopite have been known to cause excitement in inexperienced gold panners. A few tiny flakes of these micas swishing in a gold pan can produce bright bronze-colored reflections in the pan when struck by sunlight. These reflections can fool the inexperienced panner into thinking that he has found gold. removes one of these flakes from the pan and pokes it with a pin, it will break

Bornite

often called "peacock ore" because of its tarnish. Family: sulfide Formula: Cu5FeS4 Color: Reddish brown or brownish red on a fresh surface. Iridescent purple, blue, and black on a tarnished surface. Habit: massive Crystal system: Streak: grayish black Luster: submetallic to metallic Cleavage: poor Fracture: Tenacity: Hardness: 3 SG: 5-5.1 Diaphaneity: opaque Formation: occurs in igneous, metamorphic, and sedimentary rocks. Minable concentrations of bornite occur in hydrothermal veins, contact metamorphic zones, and in the enriched zone of many sulfide mineral deposits. Other: tarnishes to iridescent shades of blue, purple, red, green and yellow. It is commonly called "peacock ore" or "purple copper ore" after these iridescent colors. Upon surface exposure, bornite will weather to chalcocite or other copper minerals. Bornite is a popular and fast-selling mineral specimen at museums, mineral shows, and tourist shops. However, some material sold as "peacock ore" has a tarnish with spectacular colors - greatly exceeding what is expected on bornite. This material is frequently chalcopyrite that has been intentionally tarnished with acid. This treatment is done to produce an item that is visually appealing and sells rapidly.

Copper

one of the early metals worked by ancient people. Nuggets of the metal could be found in streams in a few areas, and its properties allowed it to be easily worked without a required processing step. Excellent conductor of electricity, used for wiring. It is also an excellent conductor of heat and is used in cooking utensils, heat sinks, and heat exchangers. Large amounts are also used to make alloys such as brass (copper and zinc) and bronze (copper, tin, and zinc). Also alloyed with precious metals such as gold and silver. Family: Native Formula: Cu Color: Copper red on a fresh surface, dull brown when tarnished Habit: Crystal system: Isometric Streak: Metallic copper red Luster: metallic Crystal Structure: Cleavage: none Fracture: Tenacity: Hardness: 2.5-3 SG: 8.9 Diaphaneity: opaque Formation: Found in the oxidized zones of copper deposits; in hydrothermal veins; in the cavities of basalt that have been in contact with hydrothermal solutions; and as pore fillings and replacements in conglomerates that have been in contact with hydrothermal solutions. It is rarely found in large quantities, thus it is seldom the primary target of a mining operation. Most produced is extracted from sulfide deposits. .

Orthoclase

one of the most abundant rock-forming minerals of the continental crust. Orthoclase is most widely known as the pink feldspar found in many granites and as the mineral assigned a hardness of "6" in the Mohs hardness scale. Family: Silicate Formula: KAlSi3O8 Color: White, gray, pink, reddish, yellow, green, colorless Habit: Crystal system: Streak: white Luster: vitreous, pearly on cleavage faces Cleavage: perfect in two directions interasecting at 90 degrees Fracture: Tenacity: Hardness: 6 SG: 2.5-2.6 Diaphaneity: translucent to transparent Formation: forms during the crystallization of a magma into intrusive igneous rocks such as granite, granodiorite, diorite, and syenite. Significant amounts of orthoclase are also found in extrusive igneous rocks such as rhyolite, dacite, and andesite. Large crystals of orthoclase are found in igneous rocks known as pegmatite. They are normally no more than a few inches in length. During physical weathering, grains of orthoclase are incorporated into sediments and sedimentary rocks such as sandstone, conglomerate, and siltstone. Chemical weathering alters orthoclase into clay minerals such as kaolinite. significant constituent of the metamorphic rocks known as gneiss and schist. These rocks most often form during regional metamorphism when granitic rocks are subjected to heat and pressure at convergent plate boundaries involving continental crust. The orthoclase in these metamorphic rocks is inherited from their igneous protoliths. Other: raw material used in the production of glass, ceramic tile, porcelain, dinnerware, bathroom fixtures, and other ceramics. It is used as an abrasive in scouring powders and polishing compounds. It is also cut as a gemstone. An adularescent gem material known as moonstone is an intergrowth of orthoclase and albite. Orthoclase is also known in igneous rocks found on the moon and on Mars. Orthoclase is an important constituent of igneous rocks brought back from the moon by astronauts. It has also been detected in the igneous rocks of Mars during analyses done by NASA's rovers. a member of the alkali feldspar series. The alkali feldspars include albite (NaAlSi3O8), anorthoclase ((Na,K)AlSi3O8), sanidine ((K,Na)AlSi3O8), orthoclase (KAlSi3O8), and microcline (KAlSi3O8).

Aragonite

one of the three most common naturally occurring crystal forms of calcium carbonate. It is formed by biological and physical processes, including precipitation from marine and freshwater environments. Family: Carbonate Formula: CaCO3 Color: white, light tan, or colorless. Habit: Varies Crystal System: Orthorhombic Streak: White Luster: Vitreous, resinous on fracture surfaces Cleavage: ADD Fracture: Subconchoidal Tenacity: Brittle Hardness: 3.5-4, SG: 2.95 Diaphaneity: translucent to transparent Formation: Often occurs as a white branching, coral-like growth. Found in caves and near hot springs. Other: Bubbles in cold hydrochloric acid.

Turquoise

opaque mineral that occurs in beautiful shades of blue, bluish green, green, and yellowish green. It has been treasured as a gemstone for thousands of years. Isolated from one another, the ancient people of Africa, Asia, South America and North America independently made it one of their preferred materials for producing gemstones, inlay, and small sculptures. Family: Phosphate, apatite group Formula: CuAl6(PO4)4(OH)8·4H2O Color: Green Habit: Crystal system: triclinic Streak: bluish white to greenish white Luster: waxy to subvitreous, dull or chalky when weathered Cleavage: perfect Fracture: Tenacity: Hardness: 5-6 SG: 2.5-2.9 Diaphaneity: opaque Formation: rarely found in well-formed crystals. Instead it is usually an aggregate of microcrystals. When the microcrystals are packed closely together, the turquoise has a lower porosity, greater durability, and polishes to a higher luster. This luster falls short of being "vitreous" or "glassy." Instead many people describe it as "waxy" or "subvitreous." Turquoise forms best in an arid climate, and that determines the geography of turquoise sources. Most of the world's turquoise rough is currently produced in the southwestern United States, China, Chile, Egypt, Iran, and Mexico. In these areas, rainfall infiltrates downward through soil and rock, dissolving small amounts of copper. When this water is later evaporated, the copper combines with aluminum and phosphorus to deposit tiny amounts of turquoise on the walls of subsurface fractures. Turquoise can also replace the rock in contact with these waters. If the replacement is complete, a solid mass of turquoise will be formed. When the replacement is less complete, the host rock will appear as a "matrix" within the turquoise. The matrix can form a "spider web," "patchy" design, or other pattern within the stone. Most of the turquoise mined in the United States is a byproduct of copper production. The large open-pit copper mines excavate down through the shallow rock units where the turquoise is formed Other: Blue minerals are rare, and that is why turquoise captures attention in the gemstone market. The most desirable color of turquoise is a sky blue or robin's-egg blue. Departure from a nice blue color is caused by small amounts of iron substituting for aluminum in the turquoise structure. The iron imparts a green tint to the turquoise in proportion to its abundance. The color of turquoise might also be altered by small amounts of iron or zinc substituting for copper in the turquoise structure. Some turquoise contains inclusions of its host rock (known as matrix) that appear as black or brown spider-webbing or patches within the material. Smart jewelry design will surround the gem with a durable bezel that protects the sides of the gem from abrasion and impact. Turquoise is often porous, with the ability to absorb liquids. Once absorbed, these liquids can damage the turquoise or alter its color. Only a small amount of turquoise that is mined today can be used to cut finished stones or make jewelry without some type of treatment. These treatments make the turquoise stable enough for cutting, durable enough for jewelry, or improve its color and marketability.

Rose Quartz

pink specimens of the mineral quartz. It is abundant, common, and found in large quantities at numerous locations around the world Family: Silicate Formula: SiO2 Color: pink Habit: Crystal system: Streak: colorless Luster: vitreous Cleavage: none Fracture: conchoidal Tenacity: Hardness: 7 SG: 2.6 Diaphaneity: Formation: massive, anhedral occurrences in hydrothermal veins and pegmatites. pink color of rose quartz is attributed to microscopic inclusions of a pink variety of the mineral dumortierite. These inclusions are usually abundant enough to make the rose quartz translucent instead of transparent. Other: Some specimens of rose quartz contain a dense network of fine inclusions that align with the gem's hexagonal crystal structure. If a cabochon is cut so that its base is perpendicular to the c-axis of the quartz crystal, the cabochon might display asterism in the form of a six-ray star. The best star stones have a vivid pink color and a distinct, symmetrical, and well-centered star

Albite

plagioclase feldspar mineral. It is the sodium endmember of the plagioclase solid solution series. It represents a plagioclase with less than 10% anorthite content. Family: Silicate Formula: NaAlSi3O8 Color: White to gray, blueish, greenish, reddish; may be chatoyant Habit: White to gray, blueish, greenish, reddish; may be chatoyant Crystal system: Triclinic Streak: White Luster: vitreous, typically pearly on cleavages Cleavage: Fracture: uneven to conchoidal Tenacity: brittle Hardness: 6-6.5 SG: 2.6-2.65 Diaphaneity: transparent to translucent Formation: granitic and pegmatite masses (often as the variety Cleavelandite), in some hydrothermal vein deposits, and forms part of the typical greenschist metamorphic facies for rocks of originally basaltic composition. Other: Albite almost always exhibits crystal twinning often as minute parallel striations on the crystal face. Albite often occurs as fine parallel segregations alternating with pink microcline in perthite as a result of exolution on cooling. There are two variants of albite, which are referred to as 'low albite' and 'high albite'; the latter is also known as 'analbite'. Although both variants are triclinic, they differ in the volume of their unit cell, which is slightly larger for the 'high' form. The 'high' form can be produced from the 'low' form by heating above 750 °C (1,380 °F) High albite can be found in meteor impact craters. Upon further heating to more than 1,050 °C (1,920 °F) the crystal symmetry changes from triclinic to monoclinic; this variant is also known as 'monalbite'. Oftentimes, potassium can replace the sodium characteristic in albite at amounts of up to 10%. When this is exceeded the mineral is then considered to be anorthoclase. Used as a gemstone, albeit semi-precious. Albite is also used by geologists as it is identified as an important rock forming mineral. There is some industrial use for the mineral such as the manufacture of glass and ceramics

Lepidolite

rare lithium-rich mica mineral that is usually pink, red, or purple in color. It is the most common lithium-bearing mineral and serves as a minor ore of lithium metal, with rubidium and cesium sometimes being byproducts. When impregnated with quartz, lepidolite is used as a minor gemstone. Flakes of lepidolite are sometimes responsible for the color of pink and red aventurine. Family: Silicate Formula: K(Li,Al3)(AlSi3)O10(OH,F)2 Color: pink, red or purple as their dominant hue. These are the expected colors of lepidolite. The mineral sometimes has a dark tone, which gives it a grayish appearance. Rare specimens of lepidolite are colorless or yellow. Manganese is the cause of color in pink, red and purple lepidolites. Habit: Crystal system: Streak: white to colorless, often sheds tiny flakes Luster: pearly to vitreous Cleavage: perfect in one direction Fracture: Tenacity: Hardness: 2.5-3.5 SG: 2.8-3 Diaphaneity: transparent to translucent Formation: an only form in geochemical environments where high concentrations of lithium are available for mineral formation. Lepidolite is a rare mineral because these geochemical situations rarely occur. The lithium ion is very small, and it does not readily substitute in other minerals. As a result, it is usually one of the last ions to form minerals during the crystallization of a subsurface magma. As other ions are depleted, the residual fluids of magma crystallization become progressively enriched with lithium. During the final stages of crystallization, there might finally be a high enough concentration of lithium present to form discrete lithium minerals such as spodumene, lepidolite, and petalite. Pegmatites, greisens, and hydrothermal quartz veins are rocks of late-stage magmatic crystallization. They are the rocks where much of the world's lithium minerals are found. In these rocks, lepidolite occurs as disseminated particles, aggregates of fine grains, "books" of flat sheets, and aggregates of curved sheets. Most deposits of lithium-bearing minerals formed by igneous processes are small pod-shaped deposits of a few hundred to a few thousand tons where hand mining and hand separation are required. Other: chemical composition that ranges in a solid solution series from that of polylithionite KLi2Al(Si4O10)(F,OH)2 to that of trilithionite K(Li1.5Al1.5)(AlSi3O10)(F,OH)2. This compositional range of lithium mica is known as the lepidolite series. most important use of lepidolite has been as a minor ore of lithium metal. This use was more important in the first half of the 1900s than it is today. Today most lithium is produced from brine and evaporite deposits in South America, where lithium can be extracted more economically. Small amounts of rubidium sometimes substitute for lithium in the lepidolite crystal lattice. When present, the rubidium can be recovered as a byproduct during the extraction of lithium. Lepidolite and pollucite, another lithium mineral that can contain significant amounts of cesium, often occur together. These minerals can be mined for lithium with cesium as a byproduct. Lepidolite is sometimes used as a source of flake mica. It is also used to make glass and as an ingredient in some enamels. Lepidolite can be used as an ornamental stone and is an important constituent in some gem materials.

Sulfur

rarely found in a pure, uncombined form at Earth's surface. An important constituent of sulfate and sulfide minerals. It occurs in the dissolved ions of many waters. It is an important constituent of many atmospheric, subsurface, and dissolved gases. It is an essential element in all living things and is in the organic molecules of all fossil fuels. Extremely flammable burning with a blue flame, low melting temperature Family: Native Formula: S Color: Yellow, Brownish-yellow to greenish-yellow Habit: massive Crystal system: orthorhombic Streak: yellow Luster: crystals are resinous to greasy, powdered is dull or earthy Crystal Structure: Cleavage: none Fracture: conchoidal Tenacity: brittle Hardness: 1.5-2.5 SG: 2-2.1 Diaphaneity: transparent to translucent Formation: forms near volcanic vents and fumaroles, where it sublimates from a stream of hot gases. Small amounts of native sulfur also form during the weathering of sulfate and sulfide minerals. largest accumulations of mineral sulfur are found in the subsurface. Many of these are in fractures and cavities associated with sulfide ore mineralization. The largest are associated with evaporite minerals, where gypsum and anhydrite yield native sulfur as a product of bacterial action. Significant amounts of sulfur have been produced from the cap rock of salt domes but this type of production is rarely done today. Other: Even though it is insoluble in water, it is one of the most versatile elements at forming compounds. Sulfur reacts and forms compounds with all elements except gold, iodine, iridium, nitrogen, platinum, tellurium, and the inert gases.

Sphalerite

six directions of perfect cleavage with faces that exhibit a resinous to adamantine luster. Sphalerite has a dispersion that exceeds that of all of the popular gems and is three times higher than the dispersion of diamond. Family: sulfide Formula: Zinc sulfide with variable amounts of iron, (Zn,Fe)S Color: Yellow, brown, black, red, green, white, colorless Habit: Crystal system: isometric Streak: White to yellowish brown, often with an odor of sulfur Luster: non metallic, submetaalic, reisonous or adamantine Cleavage: perfect, dodecagedral, 6 directions Fracture: Tenacity: Hardness: 3.5-4 SG: 3.9-4.1 Diaphaneity: transparent to translucent Formation: Found in metamorphic, igneous, and sedimentary rocks in many parts of the world. Sphalerite is the most commonly encountered zinc mineral and the world's most important ore of zinc. Many minable deposits of sphalerite are found where hydrothermal activity or contact metamorphism has brought hot, acidic, zinc-bearing fluids in contact with carbonate rocks. There, sphalerite can be deposited in veins, fractures, and cavities, or it can form as mineralizations or replacements of its host rocks. Other: from the Greek word "sphaleros" which means deceiving or treacherous. This name is in response to the many different appearances of sphalerite and because it can be challenging to identify in hand specimens. Names for sphalerite used in the past or by miners include "zinc blende," "blackjack," "steel jack," and "rosin jack."

Azurite

soft, deep-blue copper mineral produced by weathering of copper ore deposits. Often pseudomorphed to malachite and are found together frequently Family: Carbonates Formula: Cu3(CO3)2(OH)2 Color: light blue to almost black Habit: Massive, prismatic, stalactitic, tabular Crystal system: Monoclinic Streak: light blue Luster: Glossy, vitreous Cleavage: Fracture: conchoidal Tenacity: brittle Hardness: 3.5-4.0. S.G. 3.8 Diaphaneity: transparent to translucent Formation: is a secondary mineral that usually forms when carbon dioxide-laden waters descend into the Earth and react with subsurface copper ores. The carbonic acid of these waters dissolves small amounts of copper from the ore. The dissolved copper is transported with the water until it reaches a new geochemical environment. This new environment could be a location where water chemistry or temperature changes, or where evaporation occurs. Precipitation occurs in pore spaces, fractures, and cavities of the subsurface rock, resulting is massive or nodular. In rare situations, found as stalactitic and botryoidal growths. Well-formed monoclinic crystals are infrequently found. Other: dissolves in HCL with bubbles given off. It is a secondary copper mineral, used to produce copper when smelted. Was used as a blue pigment in antiquity.

Alabaster

soft, often used for carving, and is processed for plaster powder. Family: Sulfate Formula: CaSO4 . H2O Color: Clear, colorless, white, gray, yellow, red, brown Habit: Crystal system: monoclinic Streak: White Luster: Luster pearly on cleavages. Cleavage: Fracture: Tenacity: Hardness: 1.5-2 SG: Diaphaneity: Formation: Other: two different minerals: the fine-grained massive type of gypsum and the fine-grained banded type of calcite. Geologists define alabaster only as the gypsum type. Chemically, gypsum is a hydrous sulfate of calcium. Both are easy to work and slightly soluble in water. They have been used for making a variety of indoor artwork and carving, and they will not survive long outdoors. The two kinds are readily distinguished by their different hardnesses: gypsum alabaster is so soft that a fingernail scratches it (Mohs hardness 1.5 to 2), while calcite cannot be scratched in this way (Mohs hardness 3), although it yields to a knife. Moreover, calcite alabaster, being a carbonate, effervesces when treated with hydrochloric acid, while gypsum alabaster remains almost unaffected. The coarser varieties of gypsum alabaster are converted by calcination into plaster of Paris, and are sometimes known as "plaster stone".[4] The softness of alabaster enables it to be carved readily into elaborate forms, but its solubility in water renders it unsuitable for outdoor work.[4] If alabaster with a smooth, polished surface is washed with dishwashing liquid, it will become rough, dull and whiter, losing most of its translucency and lustre.[10] The finer kinds of alabaster are employed largely as an ornamental stone, especially for ecclesiastical decoration and for the rails of staircases and halls

Rock Crystal

the most abundant mineral in Earth's crust extremely resistant to weathering highly resistant to physical and chemical weathering used to make time pieces because it vibrates at a precise frequency. Two forms, the normal α-quartz and the high-temperature β-quartz, both of which are chiral. The transformation from α-quartz to β-quartz takes place abruptly at 573 °C. Determining mineral for 7. Family: Silicate Formula: SiO2 Color: colorless Habit: 6-sided prism ending in 6-sided pyramid (typical), drusy, fine-grained to microcrystalline, massive Crystal system: α-quartz: trigonal β-quartz: hexagonal Streak: white Luster: vitreous, waxy to dull when massive Cleavage: indisticnt Fracture: conchoidal Tenacity: brittle Hardness: 7 SG: 2.65 Diaphaneity: transparent to nearly opaque Formation: defining constituent of granite and other felsic igneous rocks. It is very common in sedimentary rocks such as sandstone and shale. It is a common constituent of schist, gneiss, quartzite and other metamorphic rocks.[15] Quartz has the lowest potential for weathering in the Goldich dissolution series and consequently it is very common as a residual mineral in stream sediments and residual soils. Generally a high presence of quartz suggests a "mature" rock, since it indicates the rock has been heavily reworked and quartz was the primary mineral that endured heavy weathering. While the majority of quartz crystallizes from molten magma, quartz also chemically precipitates from hot hydrothermal veins as gangue, sometimes with ore minerals like gold, silver and copper. Large crystals of quartz are found in magmatic pegmatites Other: Geological processes have occasionally deposited sands that are composed of almost 100% quartz grains. These deposits have been identified and produced as sources of high-purity silica sand. These sands are used in the glassmaking industry. Quartz sand is used in the production of container glass, flat plate glass, specialty glass, and fiberglass. an excellent abrasive material. Quartz sands and finely ground silica sand are used for sand blasting, scouring cleansers, grinding media, and grit for sanding and sawing. ery resistant to both chemicals and heat. It is therefore often used as a foundry sand. With a melting temperature higher than most metals, it can be used for the molds and cores of common foundry work. Refractory bricks are often made of quartz sand because of its high heat resistance. Quartz sand is also used as a flux in the smelting of metals. a high resistance to being crushed. In the petroleum industry, sand slurries are forced down oil and gas wells under very high pressures in a process known as hydraulic fracturing. This high pressure fractures the reservoir rocks, and the sandy slurry injects into the fractures. The durable sand grains hold the fractures open after the pressure is released. These open fractures facilitate the flow of natural gas into the well bore. vibrate at a precise frequencies. These frequencies are so precise that quartz crystals can be used to make extremely accurate time-keeping instruments and equipment that can transmit radio and television signals with precise and stable frequencies.

Muscovite

the most common mineral of the mica family. It is an important rock-forming mineral present in igneous, metamorphic, and sedimentary rocks. Like other micas it readily cleaves into thin transparent sheets. Family: Silicate Formula: KAl2(AlSi3O10)(OH)2 Color: thick specimens often appear to be black, brown, or silver in color; however, when split into thin sheets muscovite is colorless, sometimes with a tint of brown, yellow, green, or rose Habit: Crystal system: Streak: white, often sheds tiny flakes Luster: pearly to vitreous Cleavage: perfect Fracture: Tenacity: Hardness: 2.5-3 SG: 2.8-2.9 Diaphaneity: transparent to translucent Formation: found in igneous, metamorphic, and sedimentary rocks. In igneous rocks, it is a primary mineral that is especially common in granitic rocks. In granite pegmatites, muscovite is often found in large crystals with a pseudohexagonal outline. These crystals are called "books" because they can be split into paper-thin sheets. Muscovite rarely occurs in igneous rocks of intermediate, mafic, and ultramafic composition. can form during the regional metamorphism of argillaceous rocks. The heat and pressure of metamorphism transforms clay minerals into tiny grains of mica which enlarge as metamorphism progresses. Muscovite can occur as isolated grains in schist and gneiss, or it can be abundant enough that the rocks are called "mica schist" or "micaceous gneiss." Muscovite is not especially resistant to chemical weathering. It is quickly transformed into clay minerals. Tiny flakes of muscovite sometimes survive long enough to be incorporated into sediments and immature sedimentary rocks. It is evidence that these sediments and rocks have not been subjected to severe weathering Other: early use as window panes. In the 1700s it was mined for this use from pegmatites in the area around Moscow, Russia. These panes were called "muscovy glass" and that term is thought to have inspired the mineral name "muscovite." Sheet muscovite is an excellent insulator, and that makes it suitable for manufacturing specialized parts for electrical equipment. Scrap, flake, and ground muscovite are used as fillers and extenders in a variety of paints, surface treatments, and manufactured products. The pearlescent luster of muscovite makes it an important ingredient that adds "glitter" to paints, ceramic glazes, and cosmetics.

Amazonite

trade name used for a green to bluish green to greenish blue gem material that is made into cabochons, beads, and tumbled stones.. a color variety of microcline, a potassium-rich member of the feldspar mineral group. Family: Silicate Formula: KAlSi3O8 Color: Amazonite occurs in color range of bluish green, to green, and rarely, to greenish blue. These colors can be pale, almost pastel, or vivid with a high saturation. The color of amazonite is often interrupted by streaks and inclusions of white quartz or feldspar. The mineral's color is thought to be caused by trace amounts of lead. Habit: Crystal system: triclinic Streak: white Luster: vitreous. cleavage faces sometimes have a pearly luster Cleavage: perfect in two directions, cleavage planes usually interact at 90 degrees. Fracture: Tenacity: Hardness: 6-6.5 SG: 2.6-2.8 Diaphaneity: translucent to opaque Formation: Well-formed crystals of amazonite are usually found in pegmatites, veins, and other cavities. These are underground places where mineral crystals can grow without obstructions. Amazonite granite is found in a few locations. It is sometimes mined and used as a dimension stone or an ornamental stone. Lapidary-size pieces of amazonite are sometimes found while mining pegmatite. These are used for cutting cabochons, making beads, or producing tumbled stones. Other: green color is thought to be caused by trace amounts of lead. The gem was first named "Amazon stone", after the Amazon River - although there are no known occurrences near that river. used as a gem for over 2000 years. It has been found in archaeological excavations of ancient Egypt and Mesopotamia. rarely used to produce mass-market jewelry. It is rarely used because manufacturers have difficulty finding an adequate supply of gem material and because jewelry customers are not familiar with amazonite. Amazonite is occasionally seen in one-of-a-kind jewelry made by a designer who specializes in using unusual gems.

Goethite

well known since ancient times for its use as a pigment (brown ochre). Evidence has been found of its use in paint pigment samples taken from the caves of Lascaux in France. Family: Oxide Formula: α-FeO(OH) Color: Yellowish to reddish to dark brown or black Habit: radial acicular, mammillary, botryoidal, stalactitic, massive, as encrustation, as pseudomorph; may be banded or iridescent Crystal system: orthorhombic Streak: Brown, brownish yellow to orange yellow Luster: adamantine to dull Crystal Structure: Cleavage: perfect in one direction Fracture: uneven to splintery Tenacity: Hardness: 5-5.5 SG: 3.3-4.3 Diaphaneity: Formation: often forms through the weathering of other iron-rich minerals, and thus is a common component of soils, concentrated in laterite soils. Nanoparticulate authigenic goethite is a common diagenetic iron oxyhydroxide in both marine and lake sediments. The formation of goethite is marked by the oxidation state change of Fe2+ (ferrous) to Fe3+ (ferric), which allows for goethite to exist at surface conditions. Because of this oxidation state change, commonly seen as a pseudomorph. As iron-bearing minerals are brought to the zone of oxidation within the soil, the iron turns from iron(II) to iron(III). may also be precipitated by groundwater or in other sedimentary conditions, or form as a primary mineral in hydrothermal deposits. Also been found to be produced by the excretion processes of certain bacteria types. Other: Its main modern use is as an iron ore, being referred to as brown iron ore. Fine goethite specimens are rare and therefore are valued collectibles. Banded or iridescent varieties are cut and polished into cabochons for jewelry making. Perhaps the oldest known use comes from the ancient kingdom of Phrygia. In a royal tomb a body was founterm-118d believed to be King Gordias, father of the legendary King Midas. The burial shroud had been colored with a dye containing goethite, which in its original unfaded state would have made the shroud look like it was woven from gold.

Amethyst

world's most popular purple gem. It is the purple color variety of quartz that has been used in personal adornment for over 2000 years. Family: Silicate Formula: SiO2 Color: Purple Habit: 6-sided prism ending in 6-sided pyramid (typical), drusy, fine-grained to microcrystalline, massive Crystal system: hexagonal Streak: colorless Luster: vitreous Cleavage: none Fracture: conchoidal Tenacity: Hardness: 7 SG: 2.6-2.7 Diaphaneity: transparent to translucent Formation: The first step in amethyst receiving its purple color begins during crystal growth. That is when trace amounts of iron are incorporated into a growing quartz crystal. After crystallization, gamma rays, emitted by radioactive materials within the host rock, irradiate the iron to produce the purple color. The intensity of amethyst's purple color can vary from one part of the crystal to another. These color variations, known as "color zoning," are caused by varying amounts of iron being incorporated into the crystal during different stages of crystal growth. Amethyst crystals grow slowly and the composition of the fluids delivering the iron and the silica needed for crystal growth can vary. The darkest color of amethyst forms when the largest amount of iron is incorporated into the growing crystal. That is what causes color zoning. Color zoning influences the marketability and value of amethyst. Most people want a gem with a rich and uniform color. As a result, gems of uniform color - no color zoning - are the most desirable and the most valuable. Other: Grape agate is actually botryoidal amethyst. The color of amethyst can often be modified by heating. Much of the yellow to golden quartz sold as "citrine" is actually amethyst that has been modified by heating. This heating can be natural or done intentionally by people. Natural or intentional heating can also change the color of amethyst to a pale green. The proper name for this material is prasiolite; however, many sellers call it "green amethyst."

Galena

world's primary ore of lead and is mined from a large number of deposits in many countries. Freshly broken pieces exhibit perfect cleavage in three directions that intersect at 90 degrees. It has a distinct silver color and a bright metallic luster. Galena tarnishes to a dull gray. Because lead is a primary element in galena, the mineral has a high specific gravity Family: sulfide Formula: PbS Color: Fresh surfaces are bright silver in color with a bright metallic luster, tarnishes to a dull lead gray Habit: Cubic Crystal system: Isometric Streak: Fresh surfaces are bright silver in color with a bright metallic luster, tarnishes to a dull lead gray Luster: Metallic on fresh surfaces, tarnishes dull Cleavage: Perfect, cubic, three directions at right angles Fracture: Tenacity: Hardness: 2.5+ SG: 7.4-7.6 Diaphaneity: opaque Formation: It is found in igneous and metamorphic rocks in medium- to low-temperature hydrothermal veins. In sedimentary rocks it occurs as veins, breccia cements, isolated grains, and as replacements of limestone and dolostone. Other: The number one use of lead today is in the lead-acid batteries that are used to start automobiles. Lead-acid batteries are also used as standby power supplies for computer networks, communication facilities, and other critical systems. Lead is also one of the metals used in energy storage systems associated with power generation and hybrid vehicles. typical specimen of galena is about 86.6% lead and 13.4% sulfur by weight. However, some specimens of galena contain up to a few percent silver by weight. They are called "argentiferous galena" because of their silver content. In these specimens, silver can substitute for lead in the atomic structure of the galena, or it can occur in tiny grains of silver minerals included in the galena. Silver within the galena disrupts the crystal structure, which often causes the galena to have curved cleavage faces. This tiny bit of knowledge can be a powerful prospecting tool. In addition to silver, galena can contain minor amounts of antimony, arsenic, bismuth, cadmium, copper, and zinc. Sometimes selenium substitutes for sulfur in galena. Galena is very easy to smelt. plausible evidence that "heavy metal snow" - which is most likely a combination of lead sulfide (galena) and bismuth sulfide - falls on the higher elevations of Venus. Sulfur and lead among the gases erupted from volcanoes.