Rocks and Minerals/Identification List
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This is a compilation of information for the event Rocks and Minerals. Please note that while this is a good starting resource, it should not be relied on. There are many more facts about Rocks and Minerals that are not included. Please make your own fact sheets.
Rocks
Metamorphic
Gneiss (60)
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| Classification | Metamorphic |
| Composition | Light bands: Quartz, Feldspar, Muscovite, Dark bands: Hornblende, Biotite, Graphite, Garnet |
| Environment of Formation | High-grade metamorphism of Granite |
| Texture | Foliated |
| Economic Importance | Flooring, ornamental stones, gravestones, facing stones on buildings, work surfaces |
| Average Density | 2.6-2.9 |
Marble (61)
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| Classification | Metamorphic |
| Composition | Mainly metamorphosed limestone (CaCO3) |
| Environment of Formation | High-grade metamorphism of Limestone |
| Texture | Nonfoliated |
| Economic Importance | Ornamental rock, sculpture production, urban ornamentation |
| Average Density | 2.4-2.7 |
Phyllite (62)
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| Classification | Metamorphic |
| Composition | Quartz, Sericite Mica, Chlorite |
| Environment of Formation | Medium-grade metamorphism of Slate |
| Texture | Foliated |
| Economic Importance | Architecture, construction, commercial |
| Average Density | 2.7-2.8 |
Quartzite (63)
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| Classification | Metamorphic |
| Composition | Almost entirely Quartz |
| Environment of Formation | High-grade metamorphism of Sandstone |
| Texture | Nonfoliated |
| Economic Importance | Railway ballast, countertops, decorative stone |
| Average Density | 2.6-2.8 |
Garnet Schist (64)
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| Classification | Metamorphic |
| Composition | Muscovite, Biotite, Garnet, Quartz, Feldspar |
| Environment of Formation | Medium grade metamorphism of Shale, Mudstone, or Felsic Igneous rocks |
| Texture | Foliated |
| Economic Importance | Gem material host rock, construction material (rarely) |
| Average Density | 2.4-3.0 |
Mica Schist (65)
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| Classification | Metamorphic |
| Composition | Muscovite, Biotite, Garnet, Quartz, Feldspar |
| Environment of Formation | Medium grade metamorphism of Shale, Mudstone, or Felsic Igneous rocks |
| Texture | Foliated |
| Economic Importance | Gem material host rock, construction material (rarely) |
| Average Density | 2.4-3.0 |
Slate (66)
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| Classification | Metamorphic |
| Composition | Mainly Quartz and Muscovite |
| Environment of Formation | Low-grade metamorphism of Shale |
| Texture | Foliated |
| Economic Importance | roofing, flooring, flagging |
| Average Density | 2.7-2.8 |
Igneous
Andesite (67)
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| Classification | Igneous |
| Composition | Intermediate (Plagioclase Feldspar, Biotite, Pyroxene, Amphibole) |
| Environment of Formation | Extrusive, Volcanic |
| Texture | Aphanitic to Porphyritic |
| Economic Importance | Aggregate, construction |
| Average Density | 2.5-2.8 |
Basalt (68)
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| Classification | Igneous |
| Composition | Mafic (Plagioclase and Pyroxene minerals) |
| Environment of Formation | Extrusive, Volcanic |
| Texture | Aphanitic |
| Economic Importance | Aggregate, pavement, ballast |
| Average Density | 2.8-3.0 |
Diorite (69)
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| Classification | Igneous |
| Composition | Intermediate (Plagioclase Feldspar, Biotite, Pyroxene, Amphibole) |
| Environment of Formation | Intrusive, Plutonic |
| Texture | Phaneritic |
| Economic Importance | Construction stone, sculpture stone, architectural stone |
| Average Density | 2.8-3.0 |
Gabbro (70)
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| Classification | Igneous |
| Composition | Mafic (Pyroxene, Plagioclase, minor amounts of Amphibole and Olivine) |
| Environment of Formation | Intrusive, Plutonic |
| Texture | Phaneritic |
| Economic Importance | Ornamental stone, countertops, graveyard headstones |
| Average Density | 2.7-3.3 |
Granite (71)
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| Classification | Igneous |
| Composition | Felsic (Quartz, Alkali Feldspar, Plagioclase Feldspar) |
| Environment of Formation | Intrusive, Plutonic |
| Texture | Phaneritic |
| Economic Importance | Buildings, bridges, paving, monuments, countertops, ornamental stone |
| Average Density | 2.6-2.7 |
Obsidian (72)
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| Classification | Igneous |
| Composition | Felsic (Mostly Silica) |
| Environment of Formation | Extrusive |
| Texture | Glassy |
| Economic Importance | Weapons and tools (Stone Age) |
| Average Density | 2.3-2.6 |
Pegmatite (73)
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| Classification | Igneous |
| Composition | Felsic (Granite) |
| Environment of Formation | Intrusive, Plutonic |
| Texture | Phaneritic |
| Economic Importance | Host rock for rare minerals |
| Average Density | 2.6-2.8 |
Pumice (74)
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| Classification | Igneous |
| Composition | Felsic (Rhyolite) |
| Environment of Formation | Extrusive, Volcanic |
| Texture | Vesicular |
| Economic Importance | Aggregate, abrasive |
| Average Density | 0.2-0.3 |
Rhyolite (75)
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| Classification | Igneous |
| Composition | Felsic (Quartz, Sanidine, Plagioclase) |
| Environment of Formation | Extrusive, Volcanic |
| Texture | Aphanitic |
| Economic Importance | Cements |
| Average Density | 2.4-2.6 |
Scoria (76)
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| Classification | Igneous |
| Composition | Mafic (Basalt) |
| Environment of Formation | Extrusive, Volcanic |
| Texture | Vesicular |
| Economic Importance | Landscaping, drainage, barbecue grills |
| Average Density | Greater than 1 |
Sedimentary
Arkose (78)
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| Classification | Sedimentary |
| Composition | Feldspar, Quartz, Mica |
| Environment of Formation | Weathering of Feldspar rich Igneous and Metamorphic Rocks |
| Texture | Clastic |
| Economic Importance | Ornaments, building, molars |
| Average Density | 2.2-2.8 |
Breccia (80)
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| Classification | Sedimentary |
| Composition | Quartz, Feldspar, Mica, Calcite, Clay |
| Environment of Formation | Where broken, angular fragments of rock or mineral debris accumulate |
| Texture | Clastic |
| Economic Importance | Sculptures, road beds, statues |
| Average Density | 2.0-2.4 |
Chert (81)
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| Classification | Sedimentary |
| Composition | Silicon Dioxide |
| Environment of Formation | Deep marine, thin beds |
| Texture | Chemical |
| Economic Importance | Weapon, tools (past) |
| Average Density | 2.4-2.6 |
Conglomerate (82)
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| Classification | Sedimentary |
| Composition | Mineral particles such as Quartz or Feldspar, can be Sedimentary, Metamorphic, or Igneous rock fragments |
| Environment of Formation | Along a swiftly flowing stream or a beach with strong waves that carry and weather clasts |
| Texture | Clastic |
| Economic Importance | Construction industry |
| Average Density | 2.4-2.6 |
Diatomite (83)
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| Classification | Sedimentary |
| Composition | Diatomaceous Earth (Diatoms) |
| Environment of Formation | Shallow-marine environments |
| Texture | Organic |
| Economic Importance | Filter, absorbent, pest control |
| Average Density | 1.6-1.8 |
Dolostone (85)
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| Classification | Sedimentary |
| Composition | Dolomite mineral |
| Environment of Formation | Limestone marine deposits on ancient shallow seafloors |
| Texture | Chemical |
| Economic Importance | Acid neutralization, construction, source of Magnesium |
| Average Density | 2.8-9 |
Sandstone (92)
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| Classification | Sedimentary |
| Composition | Quartz, Feldspar |
| Environment of Formation | Depositional environments |
| Texture | Clastic |
| Economic Importance | Buildings, monuments, grave stones, silica for glass |
| Average Density | 2.2-2.8 |
Shale (95)
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| Classification | Sedimentary |
| Composition | Mud that is a mix of flakes of clay minerals and tiny fragments of other minerals |
| Environment of Formation | Marine environments; silt or mud is deposited in calm waters |
| Texture | Clastic |
| Economic Importance | Additive in cement, art clay products |
| Average Density | 2.4-2.8 |
Coal Varieties
Anthracite (77)
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| Classification | Sedimentary (Coal) |
| Composition | Carbon (87%) |
| Environment of Formation | Heat and pressure, from Bituminous |
| Texture | Organic |
| Economic Importance | Coal |
| Average Density | 1.1-1.4 |
Bituminous (79)
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| Classification | Sedimentary (Coal) |
| Composition | Carbon (60-80%) |
| Environment of Formation | Organic Metamorphism |
| Texture | Organic |
| Economic Importance | Coal |
| Average Density | 1.1-1.4 |
Lignite (86)
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| Classification | Sedimentary (Coal) |
| Composition | Carbon (60-70%) |
| Environment of Formation | Transformed Peat |
| Texture | Organic |
| Economic Importance | Coal |
| Average Density | 1.1-1.4 |
Limestone Varieties
Chalk (87)
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| Classification | Sedimentary (Limestone) |
| Composition | Calcium Carbonate |
| Environment of Formation | Deep marine conditions |
| Texture | Chemical |
| Economic Importance | Raising pH in soil with low pH, antacid, cleaning |
| Average Density | 2.3-2.7 |
Coquina (83)
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| Classification | Sedimentary (Limestone) |
| Composition | Calcium Carbonate/Shells |
| Environment of Formation | Near-shore environments |
| Texture | Chemical |
| Economic Importance | Paving material, fertilizer |
| Average Density | 2.3-2.7 |
Fossiliferous (89)
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| Classification | Sedimentary (Limestone) |
| Composition | Calcium Carbonate with fossil imprints |
| Environment of Formation | Shallow marine waters |
| Texture | Chemical |
| Economic Importance | Geologic clues, ornaments, jewelry |
| Average Density | 2.3-2.7 |
Oolitic (90)
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| Classification | Sedimentary (Limestone) |
| Composition | Calcium Carbonate |
| Environment of Formation | Warm, supersaturated marine water |
| Texture | Chemical |
| Economic Importance | Ornaments, limestone |
| Average Density | 2.3-2.7 |
Travertine (91)
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| Classification | Sedimentary (Limestone) |
| Composition | Calcium Carbonate |
| Environment of Formation | Precipitation of Carbonate minerals from solution in ground and surface waters |
| Texture | Chemical |
| Economic Importance | Countertops, building material |
| Average Density | 2.3-2.7 |
Minerals
Borates
Ulexite (59)
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| Classification | Borate |
| Chemical Composition | NaCa[B5O6(OH)6] · 5H2O |
| Hardness | 2.5 |
| Streak | White |
| Luster | Vitreous, silky |
| Cleavage | Prismatic, basal |
| Fracture | Splintery |
| Density | 1.955 g/cm3 |
| Mineral Habit | Articular, capillary, fibrous |
| Crystal System | Triclinic, pinacoidal |
| Environment of Formation | Borax evaporite deposits in dry lakes of arid regions |
| Economic Importance | The boron in it is mainly used for fiberglass |
Carbonates
Aragonite (5)
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| Classification | Carbonate |
| Chemical Composition | CaCO3 |
| Hardness | 3.5-4 |
| Streak | White |
| Luster | Vitreous |
| Cleavage | Prismatic, indiscernible |
| Fracture | Subconchoidal |
| Density | 2.947 g/cm3 |
| Mineral Habit | Columnar, fibrous, pseudohexagonal |
| Crystal System | Orthorhombic |
| Environment of Formation | Sedimentary formations and evaporite deposits, hot spring deposits, hydrothermal ore veins, igneous environments, and metamorphic schists. |
| Economic Importance | Used as specimens |
Azurite (7)
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| Classification | Carbonate |
| Chemical Composition | Cu3(CO3)2(OH)2 |
| Hardness | 3.5-4 |
| Streak | Light blue |
| Luster | Vitreous |
| Cleavage | Perfect, fair |
| Fracture | Conchoidal or splintery |
| Density | 3.77 g/cm3 |
| Mineral Habit | Prismatic, stalactitic, tabular |
| Crystal System | Monoclinic |
| Environment of Formation | Reaction from carbon-dioxide laden waters descending into the earth and reacting with subsurface copper ores |
| Economic Importance | Jewelry, pigment, an indicator for subsurface copper ores |
Calcite (13)
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| Classification | Carbonate |
| Chemical Composition | CaCO3 |
| Hardness | 3 |
| Streak | White |
| Luster | Vitreous |
| Cleavage | Rhombohedral |
| Fracture | Conchoidal |
| Density | 2.7102 g/cm³ |
| Mineral Habit | Crystalline, massive, stalactitic |
| Crystal System | Trigonal |
| Environment of Formation | Forms in all rock types |
| Economic Importance | Used in acid neutralization, as a low-hardness abrasive, soil conditioner, heated for the production of limestone and marble, and in monuments and calcium carbonate sorbents. |
Dolomite (19)
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| Classification | Carbonate |
| Chemical Composition | CaMg(CO3)2 |
| Hardness | 3.5-4 |
| Streak | White |
| Luster | Vitreous, pearly |
| Cleavage | Rhombohedral |
| Fracture | Subconchoidal |
| Density | 2.84 - 2.86 g/cm3 |
| Mineral Habit | Blocky, crystalline, massive |
| Crystal System | Hexagonal |
| Environment of Formation | In sedimentary rock; occasionally in high-temperature metamorphic rocks and low-temperature hydrothermal veins. |
| Economic Importance | Used in road construction, as an acid neutralizer, a source of magnesia (MgO), a feed additive for livestock, as an ingredient in the production of glass, bricks, and ceramics. |
Malachite (36)
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| Classification | Carbonates |
| Chemical Composition | Cu2(CO3)(OH)2 |
| Hardness | 3.5-4 |
| Streak | Light green |
| Luster | Vitreous, silky, dull |
| Cleavage | Basal |
| Fracture | Irregular, uneven, subconchoidal |
| Density | 3.6 - 4.05 g/cm3 |
| Mineral Habit | Botryoidal, massive, stalactitic |
| Crystal System | Monoclinic |
| Environment of Formation | In the oxidation zone of copper deposits |
| Economic Importance | Pigment gemstone, minor copper ore |
Native Elements
Copper (16)
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| Classification | Native Element |
| Chemical Composition | Cu |
| Hardness | 2.5-3 |
| Streak | Shiny copper-red |
| Luster | Metallic |
| Cleavage | None |
| Fracture | Hackly |
| Density | 8.94 - 8.95 g/cm3 |
| Mineral Habit | Arborescent, nodular |
| Crystal System | Isometric |
| Environment of Formation | Most common in volcanic basalt rocks |
| Economic Importance | Copper alloys, electricity, U.S. pennies |
Diamond (18)
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| Classification | Native Element |
| Chemical Composition | C |
| Hardness | 10 |
| Streak | Colorless |
| Luster | Adamantine |
| Cleavage | Octahedral |
| Fracture | Conchoidal |
| Density | 3.5 - 3.53 g/cm3 |
| Mineral Habit | Euhedral, granular |
| Crystal System | Isometric |
| Environment of Formation | Formed with very high temperature and pressure in the mantle |
| Economic Importance | Used in abrasives, small parts of mechanical devices, diamond windows (thin diamond membranes), jewelry |
Gold (25)
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| Classification | Native Element |
| Chemical Composition | Au |
| Hardness | 2.5-3 |
| Streak | Shiny yellow |
| Luster | Metallic |
| Cleavage | None |
| Fracture | Hackly |
| Density | 15 - 19.3 g/cm³ |
| Mineral Habit | Arborescent, granular, platy |
| Crystal System | Isometric |
| Environment of Formation | Trace amounts are found almost anywhere; there are only a few large deposits |
| Economic Importance | Mostly jewelry, then coinage and a multitude of other uses, such as electronics, medicine, dentistry, computers, awards, pigments, gilding, and optics. |
Graphite (26)
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| Classification | Native Element |
| Chemical Composition | C |
| Hardness | 1-2 |
| Streak | Metallic |
| Luster | Black |
| Cleavage | Basal |
| Fracture | Conchoidal or sectile |
| Density | 2.09 - 2.23 g/cm3 |
| Mineral Habit | Earthy, foliated, tabular |
| Crystal System | Hexagonal |
| Environment of Formation | High temperature and pressure in the upper mantle, also in metamorphic and igneous rocks |
| Economic Importance | A wide range of uses in metallurgy and manufacturing, also commonly used in pencils |
Silver (50)
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| Classification | Native Element |
| Chemical Composition | Ag |
| Hardness | 2.5-3 |
| Streak | Silver-white |
| Luster | Metallic |
| Cleavage | None |
| Fracture | Hackly |
| Density | 10.1 - 11.1 g/cm3 |
| Mineral Habit | Arborescent, dendritic, massive |
| Crystal System | Isometric |
| Environment of Formation | In volcanic basalt rocks and in hydrothermal veins and mesothermal veins. |
| Economic Importance | Used in jewelry, tableware, coins, electronics, photographic films, ornaments. |
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Sulfur (54)
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| Classification | Native Element |
| Chemical Composition | S |
| Hardness | 1.5-2.5 |
| Streak | White |
| Luster | Resinous |
| Cleavage | Imperfect |
| Fracture | Irregular, uneven, conchoidal |
| Density | 2.07 g/cm³ |
| Mineral Habit | Massive, reniform, stalactitic |
| Crystal System | Orthorhombic |
| Environment of Formation | In sedimentary environments in evaporite and salt dome deposits, in volcanic deposits in hot springs and fumaroles, and in igneous basalt rocks of recent volcanic activity. |
| Economic Importance | Mainly used to create sulfuric acid, also used for hydrogen sulfide, insecticides, herbicides, fungicides, pharmaceuticals, soaps, textiles, papers, processed rubber, gunpowder, leather, paint, dyes, food preservatives. |
Halides
Fluorite (22)
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| Classification | Halide |
| Chemical Composition | CaF2 |
| Hardness | 4 |
| Streak | White |
| Luster | Vitreous |
| Cleavage | Perfect |
| Fracture | Splintery, sub-conchoidal |
| Density | 3.175 - 3.56 g/cm3 |
| Mineral Habit | Crystalline, disseminated, massive, granular |
| Crystal System | Isometric |
| Environment of Formation | Hydrothermal ore veins, sedimentary deposits, metamorphic environments, and pegmatite dikes. |
| Economic Importance | Used in a wide variety of chemical, metallurgical, and ceramic processes. |
Halite (30)
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| Classification | Halide |
| Chemical Composition | NaCl |
| Hardness | 2.5 |
| Streak | White |
| Luster | Vitreous |
| Cleavage | Perfect |
| Fracture | Conchoidal |
| Density | 2.168 g/cm3 |
| Mineral Habit | Crystalline, euhedral, granular |
| Crystal System | Isometric |
| Environment of Formation | Evaporite deposits, sedimentary salt beds, and salt domes. |
| Economic Importance | Crushed and used to control snow/ice, used as a nutrient, sed by the chemical industry. |
Oxides/Hydroxides
Bauxite (8)
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| Classification | Hydroxide |
| Chemical Composition | AlO(OH) |
| Hardness | 1-3 |
| Streak | White |
| Luster | Dull |
| Cleavage | None |
| Fracture | Earthy |
| Density | Approximately 3 g/cm3 |
| Mineral Habit | Massive, pisolitic |
| Crystal System | Amorphous |
| Environment of Formation | In the weathered surface zones in clay deposits and limestones, as well as low-silica igneous rocks |
| Economic Importance | Aluminum ore, oilfield proppant |
Corundum (17)
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| Classification | Oxide |
| Chemical Composition | Al2O3 |
| Hardness | 9 |
| Streak | Colorless |
| Luster | Vitreous, adamantine |
| Cleavage | None (commonly exhibits rhombohedral and basal parting) |
| Fracture | Irregular, uneven, conchoidal |
| Density | 3.98 - 4.1 g/cm3 |
| Mineral Habit | Euhedral, prismatic, tabular |
| Crystal System | Hexagonal |
| Environment of Formation | In altered metamorphic rocks. |
| Economic Importance | Used as an abrasive and commonly in jewelry. |
Goethite/Limonite (21)
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| Classification | Hydroxide/Oxide |
| Chemical Composition | FeO(OH)·nH2O |
| Hardness | 4-5.5 |
| Streak | Yellow to brown |
| Luster | Silky, dull |
| Cleavage | None |
| Fracture | Irregular, uneven |
| Density | 2.7 - 4.3 g/cm³ |
| Mineral Habit | Acicular, radial, reniform |
| Crystal System | Orthorhombic |
| Environment of Formation | Made from weathering of iron-bearing materials |
| Economic Importance | Pigment and minor iron ore |
Hematite (31)
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| Classification | Oxide |
| Chemical Composition | Fe2O3 |
| Hardness | 5-6 |
| Streak | Red, reddish-brown |
| Luster | Metallic, dull, earthy |
| Cleavage | None (occasionally exhibits rhombohedral and basal parting) |
| Fracture | Uneven |
| Density | 5.26 g/cm³ |
| Mineral Habit | Tabular, earthy, blocky |
| Crystal System | Trigonal |
| Environment of Formation | Found in all rock types |
| Economic Importance | Most important iron ore |
Magnetite (45)
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| Classification | Oxide |
| Chemical Composition | Fe3O4 |
| Hardness | 5.5-6.5 |
| Streak | Black |
| Luster | Metallic |
| Cleavage | None |
| Fracture | Subconchoidal, even |
| Density | 5.175 g/cm³ |
| Mineral Habit | Crystalline, massive, granular |
| Crystal System | Isometric |
| Environment of Formation | Occurs in igneous and metamorphic rocks |
| Economic Importance | Used as iron ore and to study the earth's magnetic field |
Phosphates
Apatite (4)
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| Classification | Phosphate group |
| Chemical Composition | Ca5(PO4)3(F,Cl,OH) |
| Hardness | 5 |
| Streak | White |
| Luster | Vitreous |
| Cleavage | Indiscernible |
| Fracture | Conchoidal |
| Density | 3.1 - 3.2 g/cm3 |
| Mineral Habit | Earthy, colloform, massive, granular |
| Crystal System | Hexagonal |
| Environment of Formation | In every rock type |
| Economic Importance | Fertilizer, phosphoric acid, hydrofluoric acid, gemstones, an ore of rare earth elements, pigments |
Sulfates
Barite (9)
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| Classification | Sulfate |
| Chemical Composition | BaSO4 |
| Hardness | 3-3.5 |
| Streak | White |
| Luster | Vitreous, pearly |
| Cleavage | Basal, prismatic, pinacoidal |
| Fracture | Irregular, uneven |
| Density | 4.5 g/cm3 |
| Mineral Habit | Massive, prismatic, tabular |
| Crystal System | Orthorhombic |
| Environment of Formation | Often replaces other minerals in sedimentary rock layers and in hydrothermal and mesothermal metal ore veins |
| Economic Importance | Drilling mud; high-density filler for paper, rubber, plastics |
Celestite (14)
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| Classification | Sulfate |
| Chemical Composition | SrSO4 |
| Hardness | 3-3.5 |
| Streak | White |
| Luster | Vitreous, pearly |
| Cleavage | Basal, prismatic, pinacoidal |
| Fracture | Uneven |
| Density | 3.96 - 3.98 g/cm3 |
| Mineral Habit | Crystalline, granular, massive |
| Crystal System | Orthorhombic |
| Environment of Formation | In sedimentary rock |
| Economic Importance | Strontium ore; popular among collectors |
Gypsum Varieties
Alabaster (27)
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| Classification | Sulfate (gypsum variety) |
| Chemical Composition | CaSO4 · 2H2O |
| Hardness | 2 |
| Streak | White |
| Luster | Vitreous, pearly |
| Cleavage | Perfect, distinct |
| Fracture | Uneven |
| Density | Approximately 2.3 g/cm3 |
| Mineral Habit | Massive |
| Crystal System | Monoclinic |
| Environment of Formation | Found in layered sedimentary deposits and as an evaporite |
| Economic Importance | Used in plaster, drywall, and cement |
Satin Spar (28)
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| Classification | Sulfate (Gypsum variety) |
| Chemical Composition | CaSO4 · 2H2O |
| Hardness | 2 |
| Streak | White |
| Luster | Silky, pearly |
| Cleavage | None |
| Fracture | Granular |
| Density | 2.312 - 2.322 g/cm3 |
| Mineral Habit | Fibrous |
| Crystal System | Monoclinic |
| Environment of Formation | Found in layered sedimentary deposits and as an evaporite |
| Economic Importance | Used in plaster, drywall, and cement |
Selenite (29)
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|---|---|
| Classification | Sulfate (gypsum variety) |
| Chemical Composition | CaSO4 · 2H2O |
| Hardness | 2 |
| Streak | White |
| Luster | Vitreous, pearly |
| Cleavage | None |
| Fracture | Uneven |
| Density | 2.312 - 2.322 g/cm3 |
| Mineral Habit | Fibrous |
| Crystal System | Monoclinic |
| Environment of Formation | Found in layered sedimentary deposits and as an evaporite |
| Economic Importance | Used in plaster, drywall, and cement |
Sulfides
Bornite (12)
| Picture | |
|---|---|
| Classification | Sulfide |
| Chemical Composition | Cu5FeS4 |
| Hardness | 3 |
| Streak | Dark grey to black |
| Luster | Metallic |
| Cleavage | Indescribable |
| Fracture | Conchoidal |
| Density | 5.06 - 5.09 g/cm3 |
| Mineral Habit | Granular, massive, reniform |
| Crystal System | Orthorhombic |
| Environment of Formation | In copper ore veins and hydrothermal metamorphic rocks |
| Economic Importance | Ore of copper |
Chalcopyrite (15)
| Picture | |
|---|---|
| Classification | Sulfide |
| Chemical Composition | CuFeS2 |
| Hardness | 3.5-4 |
| Streak | Black with a greenish tint |
| Luster | Metallic |
| Cleavage | Poor, indistinct/indiscernible |
| Fracture | Uneven |
| Density | 4.1-4.3 g/cm3 |
| Mineral Habit | Druse, euhedral, striated |
| Crystal System | Tetragonal |
| Environment of Formation | In the sulfide zones of copper deposits |
| Economic Importance | Most important copper ore |
Galena (23)
| Picture | |
|---|---|
| Classification | Sulfide |
| Chemical Composition | PbS |
| Hardness | 2.5-3 |
| Streak | Steel grey |
| Luster | Metallic |
| Cleavage | Cubic |
| Fracture | Subconchoidal |
| Density | 7.58 g/cm3 |
| Mineral Habit | Euhedral, granular, massive |
| Crystal System | Isometric |
| Environment of Formation | In various igneous, metamorphic, and sedimentary deposits |
| Economic Importance | Lead ore |
Pyrite (40)
| Picture | |
|---|---|
| Classification | Sulfide |
| Chemical Composition | FeS2 |
| Hardness | 6-6.5 |
| Streak | Black with a slightly green tinge |
| Luster | Metallic |
| Cleavage | None |
| Fracture | Conchoidal |
| Density | 4.8-5 g/cm3 |
| Mineral Habit | Druse, stalactitic, striated |
| Crystal System | Isometric |
| Environment of Formation | Forms at high and low temperatures and small quantities in all rock types |
| Economic Importance | Ore/indicator of gold |
Sphalerite (52)
| Picture | |
|---|---|
| Classification | Sulfide |
| Chemical Composition | ZnS |
| Hardness | 3.5-4 |
| Streak | White, light brown |
| Luster | Resinous |
| Cleavage | All sides form a dodecahedron |
| Fracture | Conchoidal |
| Density | 3.9-4.1 g/cm3 |
| Mineral Habit | Colloform, euhedral, granular |
| Crystal System | Isometric |
| Environment of Formation | In sedimentary limestone deposits, hypothermal veins and mesothermal veins, and in hydrothermal replacement deposits. |
| Economic Importance | Primary zinc ore, also used as a specimen |
Silicates
Beryl (10)
| Picture | |
|---|---|
| Classification | Silicate |
| Chemical Composition | Be3Al2Si6O18 |
| Hardness | 7.5-8 |
| Streak | Colorless |
| Luster | Vitreous, waxy |
| Cleavage | Basal |
| Fracture | Uneven, conchoidal |
| Density | 2.63 - 2.92 g/cm3 |
| Mineral Habit | Columnar, crystalline, prismatic |
| Crystal System | Hexagonal |
| Environment of Formation | Mainly occurs in granite, rhyolite, and pegmatite |
| Economic Importance | Gemstones, a minor ore of beryllium |
Epidote (20)
| Picture | |
|---|---|
| Classification | Silicate |
| Chemical Composition | Ca2(Al2,Fe)(SiO4)(Si2O7)O(OH) |
| Hardness | 6-7 |
| Streak | White to colorless |
| Luster | Vitreous, pearly, resinous |
| Cleavage | Perfect |
| Fracture | Uneven |
| Density | 3.3 - 3.6 g/cm3 |
| Mineral Habit | Fibrous, massive, prismatic |
| Crystal System | Monoclinic |
| Environment of Formation | Found in igneous and metamorphic rocks |
| Economic Importance | Minor gemstone use |
Kaolinite (33)
| Picture | |
|---|---|
| Classification | Silicate |
| Chemical Composition | Al2Si2O5(OH)4 |
| Hardness | 2-2.5 |
| Streak | White |
| Luster | Dull, earthy |
| Cleavage | Perfect |
| Fracture | Earthy |
| Density | 2.65 g/cm3 |
| Mineral Habit | Earthy |
| Crystal System | Monoclinic |
| Environment of Formation | As an altering mineral in igneous, metamorphic, and sedimentary environments |
| Economic Importance | Used in pottery, ceramics, paper production, and some medicines |
Olivine (38)
| Picture | |
|---|---|
| Classification | Silicate |
| Chemical Composition | (Mg,Fe)2SiO4 |
| Hardness | 6.5-7 |
| Streak | Colorless |
| Luster | Vitreous |
| Cleavage | Poor |
| Fracture | Conchoidal |
| Density | 3.2-3.4 g/cm3 |
| Mineral Habit | Massive, granular |
| Crystal System | Orthorhombic |
| Environment of Formation | Found in dark, igneous rocks |
| Economic Importance | Gemstones, part of earth's mantle, a mineral of peridot |
Sodalite (51)
| Picture | |
|---|---|
| Classification | Silicate |
| Chemical Composition | Na8(Al6Si6O24)Cl2 |
| Hardness | 5.5-6 |
| Streak | White |
| Luster | Vitreous, greasy |
| Cleavage | Poor |
| Fracture | Uneven, conchoidal |
| Density | 2.2-2.3 |
| Mineral Habit | Massive, disseminated, granular |
| Crystal System | Isometric |
| Environment of Formation | Mostly in igneous rocks that crystallized from sodium-rich magma |
| Economic Importance | Semiprecious gemstone; cheaper alternative to lapis lazuli |
Staurolite (53)
| Picture | |
|---|---|
| Classification | Silicate |
| Chemical Composition | (Fe,Mg,Zn,Li)2Al9Si4O22(OH)2 |
| Hardness | 7-7.5 |
| Streak | White |
| Luster | Vitreous, dull |
| Cleavage | Distinct |
| Fracture | Uneven, subconchoidal |
| Density | 3.7-3.8 g/cm3 |
| Mineral Habit | Tabular, twinning is common |
| Crystal System | Monoclinic |
| Environment of Formation | In metamorphosed schists, gneisses, and shales |
| Economic Importance | Used in geologic field work to assess a rock's metamorphic history |
Talc (55)
| Picture | |
|---|---|
| Classification | Silicate |
| Chemical Composition | Mg3Si4O10(OH)2 |
| Hardness | 1 |
| Streak | White |
| Luster | Greasy, waxy, pearly |
| Cleavage | Perfect |
| Fracture | Uneven |
| Density | 2.7-2.8 g/cm3 |
| Mineral Habit | Foliated, massive, scaly |
| Crystal System | Monoclinic |
| Environment of Formation | In metamorphic rocks |
| Economic Importance | Used in plastics, ceramics, cosmetics, paper, paint, roofing, and rubber |
Topaz (56)
| Picture | |
|---|---|
| Classification | Silicate |
| Chemical Composition | Al2SiO4(F,OH)2 |
| Hardness | 8 |
| Streak | Colorless |
| Luster | Vitreous |
| Cleavage | Basal |
| Fracture | Subconchoidal |
| Density | 3.4-3.6 g/cm3 |
| Mineral Habit | Crystalline, massive, prismatic |
| Crystal System | Orthorhombic |
| Environment of Formation | Generally formed in granites, pegmatites, and rhyolites |
| Economic Importance | Gemstone |
Tourmaline Group (57)
| Picture | |
|---|---|
| Classification | Silicate group |
| Chemical Composition | (Ca,Na,K,)(Li,Mg,Fe+2,Fe+3,Mn+2,Al,Cr+3,V+3)3(Mg,Al,Fe+3,V+3,Cr+3)6((Si,Al,B)6O18)(BO3)3(OH,O)3(OH,F,O) |
| Hardness | 7-7.5 |
| Streak | White to colorless |
| Luster | Vitreous |
| Cleavage | Indistinct |
| Fracture | Irregular, uneven, conchoidal |
| Density | 2.9-3.1 g/cm3 |
| Mineral Habit | Prismatic |
| Crystal System | Hexagonal |
| Environment of Formation | Formed in granites, pegmatites, rhyolites, and some metamorphic environments |
| Economic Importance | Popular gemstone and specimen |
Amphibole Group
Hornblende (32)
| Picture | |
|---|---|
| Classification | Silicate (Amphibole) |
| Chemical Composition | (Ca,Na)2-3(Mg,Fe,Al)5(Si,Al)8O22(OH,F)2 |
| Hardness | 5-6 |
| Streak | Colorless |
| Luster | Vitreous, submetallic, dull |
| Cleavage | Prismatic |
| Fracture | Uneven, splintery |
| Density | 2.9-3.4 g/cm3 |
| Mineral Habit | Prismatic, tabular, platy |
| Crystal System | Monoclinic |
| Environment of Formation | Found in metamorphic and igneous environments |
| Economic Importance | Constituent of granite |
Tremolite (58)
| Picture | |
|---|---|
| Classification | Silicate (Amphibole) |
| Chemical Composition | Ca2(Mg,Fe)5Si8O22(OH)2 |
| Hardness | 5-6 |
| Streak | Colorless |
| Luster | Vitreous, silky |
| Cleavage | Prismatic |
| Fracture | Uneven, splintery |
| Density | 2.9-3.2 |
| Mineral Habit | Columnar, massive, fibrous, granular |
| Crystal System | Monoclinic |
| Environment of Formation | Found in igneous and metamorphic environments |
| Economic Importance | Used in asbestos |
Feldspar - Plagioclase
Albite (1)
| Picture | |
|---|---|
| Classification | Silicate (Plagioclase Feldspar) |
| Chemical Composition | NaAlSi3O8 |
| Hardness | 6-6.5 |
| Streak | White |
| Luster | Vitreous, pearly |
| Cleavage | Basal, prismatic, pinacoidal |
| Fracture | Subconchoidal, uneven |
| Density | 2.6-2.63 |
| Mineral Habit | Blocky, granular, striated |
| Crystal System | Triclinic |
| Environment of Formation | Most often found in granites and pegmatites |
| Economic Importance | Used in the manufacture of ceramics |
Feldspar - Potassium
Amazonite/Microcline (3)
| Picture | |
|---|---|
| Classification | Silicate (Potassium Feldspar) |
| Chemical Composition | KAlSi3O8 |
| Hardness | 6 |
| Streak | White |
| Luster | Vitreous |
| Cleavage | Basal, prismatic, pinacoidal |
| Fracture | Conchoidal, uneven |
| Density | 2.56-2.58 g/cm3 |
| Mineral Habit | Blocky, crystalline, prismatic |
| Crystal System | Triclinic |
| Environment of Formation | Found in pegmatites, metamorphic rocks, hydrothermal veins, and sedimentary conglomerates |
| Economic Importance | Used in glass, ceramics, and jewelry |
Orthoclase/Microcline (21)
| Picture | |
|---|---|
| Classification | Silicate (Potassium Feldspar) |
| Chemical Composition | KAlSi3O8 |
| Hardness | 6 |
| Streak | White |
| Luster | Vitreous, pearly |
| Cleavage | Basal, prismatic, pinacoidal |
| Fracture | Conchoidal, uneven |
| Density | 2.6 g/cm3 |
| Mineral Habit | Blocky, massive, granular, prismatic |
| Crystal System | Monoclinic |
| Environment of Formation | Low-temperature metamorphic rocks, pegmatites, and conglomerates |
| Economic Importance | Used for glass, ceramics, and gemstones |
Garnet Group
Almandine (2)
| Picture | |
|---|---|
| Classification | Silicate (Garnet) |
| Chemical Composition | Fe3Al2Si3O12 |
| Hardness | 7.5-8.5 |
| Streak | Colorless |
| Luster | Vitreous |
| Cleavage | None (may exhibit parting) |
| Fracture | Conchoidal, uneven |
| Density | 4.3 g/cm3 |
| Mineral Habit | Granular, massive, lamellar |
| Crystal System | Isometric |
| Environment of Formation | In regional metamorphic mica schist, contact metamorphic hornfels, diorite and granite pegmatites, and alluvial deposits |
| Economic Importance | Used as an abrasive and a gemstone |
Mica Group
Biotite (11)
| Picture | |
|---|---|
| Classification | Silicate (Mica) |
| Chemical Composition | K(Mg,Fe2+3)(Al,Fe3+)Si3O10(OH,F)2 |
| Hardness | 2.5-3 |
| Streak | White |
| Luster | Pearly |
| Cleavage | Perfect |
| Fracture | Uneven |
| Density | 2.8 - 3.4 g/cm3 |
| Mineral Habit | Lamellar, micaceous, pseudo-hexagonal |
| Crystal System | Monoclinic |
| Environment of Formation | Formed in metamorphic and igneous rocks; the primary mineral of rare earth pegmatites |
| Economic Importance | Used in paints, in rubber products, and to date igneous rocks |
Lepidolite (34)
| Picture | |
|---|---|
| Classification | Silicate (Mica) |
| Chemical Composition | K(Li,Al)3(Si,Al)4O10(F,OH)2 |
| Hardness | 2.5-3 |
| Streak | White |
| Luster | Pearly |
| Cleavage | Perfect |
| Fracture | Uneven |
| Density | 2.8 - 2.9 g/cm3 |
| Mineral Habit | Micaceous, pseudo-hexagonal |
| Crystal System | Monoclinic |
| Environment of Formation | Formed in high-lithium granite pegmatites |
| Economic Importance | Most important lithium-bearing mineral; a secondary source of it |
Muscovite (37)
| Picture | |
|---|---|
| Classification | Silicate (Mica) |
| Chemical Composition | KAl3Si3O10(OH)2 |
| Hardness | 2-2.5 |
| Streak | Colorless |
| Luster | Pearly |
| Cleavage | Perfect |
| Fracture | Uneven |
| Density | 2.7-3 g/cm3 |
| Mineral Habit | Micaceous, foliated, massive |
| Crystal System | Monoclinic |
| Environment of Formation | Mostly in granite pegmatites, contact metamorphic rocks, metamorphic schists, and hydrothermal veins |
| Economic Importance | Used in paint, rubber, drilling mud, and roofing |
Pyroxene Group
Augite (6)
| Picture | |
|---|---|
| Classification | Silicate (Pyroxene) |
| Chemical Composition | (Ca,Na)(Mg,Fe,Al)(Al,Si)2O6 |
| Hardness | 5-6 |
| Streak | Light green to colorless |
| Luster | Vitreous, dull |
| Cleavage | Prismatic (may exhibit parting) |
| Fracture | Uneven |
| Density | 3.2-3.6 |
| Mineral Habit | Columnar, granular, massive |
| Crystal System | Monoclinic |
| Environment of Formation | Mainly in igneous environments |
| Economic Importance | No commercial uses |
Rhodonite (49)
| Picture | |
|---|---|
| Classification | Silicate (Pyroxene) |
| Chemical Composition | MnSiO3 |
| Hardness | 5.5-6 |
| Streak | Colorless |
| Luster | Vitreous |
| Cleavage | Perfect |
| Fracture | Hackly, uneven |
| Density | 3.4-3.7 g/cm3 |
| Mineral Habit | Massive, granular, tabular |
| Crystal System | Triclinic |
| Environment of Formation | Manganese-rich metamorphic environments and hydrothermal replacement deposits |
| Economic Importance | Decorative uses, jewelry; minor manganese ore |
Quartz Varieties
Agate/Onyx (41)
| Picture | |
|---|---|
| Classification | Silicate (Quartz variety) |
| Chemical Composition | SiO2 |
| Hardness | 7 |
| Streak | White |
| Luster | Vitreous |
| Cleavage | None |
| Fracture | Conchoidal |
| Density | 2.6 g/cm3 |
| Mineral Habit | Crystalline, druse |
| Crystal System | Hexagonal |
| Environment of Formation | Occurs in all mineral environments |
| Economic Importance | Used in electronics, glass, abrasives, and sand |
Amethyst (42)
| Picture | |
|---|---|
| Classification | Silicate (Quartz variety) |
| Chemical Composition | SiO2 |
| Hardness | 7 |
| Streak | White |
| Luster | Vitreous |
| Cleavage | None |
| Fracture | Conchoidal |
| Density | 2.6 g/cm3 |
| Mineral Habit | Crystalline, druse |
| Crystal System | Hexagonal |
| Environment of Formation | Occurs in all mineral environments |
| Economic Importance | Used in electronics, glass, abrasives, and sand |
Chalcedony (43)
| Picture | |
|---|---|
| Classification | Silicate (Quartz variety) |
| Chemical Composition | SiO2 |
| Hardness | 7 |
| Streak | White |
| Luster | Vitreous |
| Cleavage | None |
| Fracture | Conchoidal |
| Density | 2.6 g/cm3 |
| Mineral Habit | Crystalline, druse |
| Crystal System | Hexagonal |
| Environment of Formation | Occurs in all mineral environments |
| Economic Importance | Used in electronics, glass, abrasives, and sand |
Citrine (44)
| Picture | |
|---|---|
| Classification | Silicate (Quartz variety) |
| Chemical Composition | SiO2 |
| Hardness | 7 |
| Streak | White |
| Luster | Vitreous |
| Cleavage | None |
| Fracture | Conchoidal |
| Density | 2.6 g/cm3 |
| Mineral Habit | Crystalline, druse |
| Crystal System | Hexagonal |
| Environment of Formation | Occurs in all mineral environments |
| Economic Importance | Used in electronics, glass, abrasives, and sand |
Crystal (45)
| Picture | |
|---|---|
| Classification | Silicate (Quartz variety) |
| Chemical Composition | SiO2 |
| Hardness | 7 |
| Streak | White |
| Luster | Vitreous |
| Cleavage | None |
| Fracture | Conchoidal |
| Density | 2.6 g/cm3 |
| Mineral Habit | Crystalline, druse |
| Crystal System | Hexagonal |
| Environment of Formation | Occurs in all mineral environments |
| Economic Importance | Used in electronics, glass, abrasives, and sand |
Jasper (46)
| Picture | |
|---|---|
| Classification | Silicate (Quartz variety) |
| Chemical Composition | SiO2 |
| Hardness | 7 |
| Streak | White |
| Luster | Vitreous |
| Cleavage | None |
| Fracture | Conchoidal |
| Density | 2.6 g/cm3 |
| Mineral Habit | Crystalline, druse |
| Crystal System | Hexagonal |
| Environment of Formation | Occurs in all mineral environments |
| Economic Importance | Used in electronics, glass, abrasives, and sand |
Milky Quartz (47)
| Picture | |
|---|---|
| Classification | Silicate (Quartz variety) |
| Chemical Composition | SiO2 |
| Hardness | 7 |
| Streak | White |
| Luster | Vitreous |
| Cleavage | None |
| Fracture | Conchoidal |
| Density | 2.6 g/cm3 |
| Mineral Habit | Crystalline, druse |
| Crystal System | Hexagonal |
| Environment of Formation | Occurs in all mineral environments |
| Economic Importance | Used in electronics, glass, abrasives, and sand |
Opal (38)
| Picture | |
|---|---|
| Classification | Silicate (Quartz variety) |
| Chemical Composition | SiO2*nH2O |
| Hardness | 5.5-6.5 |
| Streak | White |
| Luster | Vitreous |
| Cleavage | None |
| Fracture | Conchoidal |
| Density | 2.09 g/cm3 |
| Mineral Habit | Crystalline, druse |
| Crystal System | Amorphous |
| Environment of Formation | Occurs in all mineral environments |
| Economic Importance | Used in electronics, glass, abrasives, and sand |
Rose Quartz (48)
| Picture | |
|---|---|
| Classification | Silicate (Quartz variety) |
| Chemical Composition | SiO2 |
| Hardness | 7 |
| Streak | White |
| Luster | Vitreous |
| Cleavage | None |
| Fracture | Conchoidal |
| Density | 2.6 g/cm3 |
| Mineral Habit | Crystalline, druse |
| Crystal System | Hexagonal |
| Environment of Formation | Occurs in all mineral environments |
| Economic Importance | Used in electronics, glass, abrasives, and sand |
National List
Actinolite
| Picture | |
|---|---|
| Classification | Silicate (Amphibole) |
| Chemical Composition | Ca2(Mg,Fe)5Si8O22(OH)2 |
| Hardness | 5.5-6 |
| Streak | Colorless |
| Luster | Vitreous, silky |
| Cleavage | Prismatic |
| Fracture | Uneven, splintery |
| Density | 2.9-3.5 |
| Mineral Habit | Fibrous, splintery |
| Crystal System | Monoclinic |
| Environment of Formation | Metamorphic & Igneous rocks, Serpentine deposits, hydrothermal replacement deposits |
| Economic Importance | Gemstone, asbestos |
Kyanite
| Picture | |
|---|---|
| Classification | Silicate |
| Chemical Composition | Al2SiO5 |
| Hardness | Anisotropic- vertical: 4.5-5.5; horizontal: 6-7 |
| Streak | White to colorless |
| Luster | Vitreous, pearly |
| Cleavage | Perfect |
| Fracture | Splintery |
| Density | 3.5-3.7 g/cm3 |
| Mineral Habit | Columnar, fibrous |
| Crystal System | Triclinic |
| Environment of Formation | Found mainly in metamorphic rocks |
| Economic Importance | Used in industries that require heat resistance, such as railroads |
Labradorite
| Picture | |
|---|---|
| Classification | Silicate (Plagioclase Feldspar) |
| Chemical Composition | (Na,Ca)(Al,Si)4O8 |
| Hardness | 6-6.5 |
| Streak | White |
| Luster | Vitreous, pearly |
| Cleavage | Basal, prismatic, pinacoidal |
| Fracture | Conchoidal, uneven |
| Density | 2.6-2.8 g/cm3 |
| Mineral Habit | Crystalline, granular, striated |
| Crystal System | Triclinic |
| Environment of Formation | Found in sedimentary deposits made from the weathering of igneous or metamorphic rocks that contain feldspar |
| Economic Importance | Architectural stone, gemstone, cabochon |
Pyrolusite
| Picture | |
|---|---|
| Classification | Oxide |
| Chemical Composition | MnO2 |
| Hardness | 6-6.5 |
| Streak | Bluish-black to black |
| Luster | Metallic, dull, earthy |
| Cleavage | Perfect |
| Fracture | Splintery, uneven |
| Density | 4.4-5.3 g/cm3 |
| Mineral Habit | Dendritic, earthy, reniform |
| Crystal System | Tetragonal |
| Environment of Formation | Oxidation product of weathered manganese minerals, also forms from stagnant shallow bog and swamp deposits |
| Economic Importance | Major manganese ore |
Rhodochrosite
| Picture | |
|---|---|
| Classification | Carbonate |
| Chemical Composition | MnCO3 |
| Hardness | 3.5-4 |
| Streak | White |
| Luster | Vitreous to pearly |
| Cleavage | Rhombohedral |
| Fracture | Conchoidal to even |
| Density | 3.3-3.6 |
| Mineral Habit | Rhombohedral and Scalenohedral crystals |
| Crystal System | Hexagonal |
| Environment of Formation | Hydrothermal veins, igneous Pegmatites |
| Economic Importance | Gemstone, ore of Manganese |
Rutile
| Picture | |
|---|---|
| Classification | Oxide |
| Chemical Composition | TiO2 |
| Hardness | 6-6.5 |
| Streak | White to light brown |
| Luster | Adamantine, submetallic |
| Cleavage | Basal |
| Fracture | Uneven |
| Density | 4.2-4.3 |
| Mineral Habit | Prismatic, acicular |
| Crystal System | Tetragonal |
| Environment of Formation | Igneous, Metamorphic |
| Economic Importance | Titanium ore, white pigment |
Spodumene
| Picture | |
|---|---|
| Classification | Silicate (Pyroxene) |
| Chemical Composition | LiAlSi2O6 |
| Hardness | 6.5-7 |
| Streak | White |
| Luster | Vitreous, silky |
| Cleavage | Prismatic |
| Fracture | uneven, splintery |
| Density | 3.1-3.2 |
| Mineral Habit | Prismatic |
| Crystal System | Monoclinic |
| Environment of Formation | Lithium Pegmatites |
| Economic Importance | Lithium ore, gemstones |
Stilbite
| Picture | |
|---|---|
| Classification | Silicate (Zeolite) |
| Chemical Composition | (Na,Ca,K)4-9Al9Si27O72 · n(H2O) |
| Hardness | 3.5-4 |
| Streak | Colorless |
| Luster | Vitreous, pearly, dull |
| Cleavage | Perfect |
| Fracture | Uneven |
| Density | 2.1-2.2 |
| Mineral Habit | Tabular, platy |
| Crystal System | Monoclinic |
| Environment of Formation | Igneous, Metamorphic |
| Economic Importance | Chemical filters, ornament |
Turquoise
| Picture | |
|---|---|
| Classification | Phosphate |
| Chemical Composition | CuAl6(PO4)4(OH)8•4(H2O) |
| Hardness | 5-6 |
| Streak | Bluish-greenish-white |
| Luster | Waxy |
| Cleavage | Perfect |
| Fracture | Conchoidal |
| Density | 2.6-2.8 |
| Mineral Habit | Concretionary, encrustations, massive |
| Crystal System | Triclinic |
| Environment of Formation | As an alteration mineral in hydrothermal replacement deposits, usually in arid copper-bearing regions; in sedimentary and metamorphic rocks |
| Economic Importance | Mainly jewelry |
Zircon
| Picture | |
|---|---|
| Classification | Silicates |
| Chemical Composition | ZrSiO4 |
| Hardness | 7.5 |
| Streak | Colorless |
| Luster | Vitreous, adamantine |
| Cleavage | Poor, indistinct |
| Fracture | Conchoidal, uneven |
| Density | 4.6-4.7 g/cm3 |
| Mineral Habit | Crystalline, prismatic, tabular |
| Crystal System | Tetragonal |
| Environment of Formation | Most often in igneous environments, usually in pegmatites; also in high-grade metamorphic rocks |
| Economic Importance | Ore of zirconium metal, ore of zirconium dioxide, whitening agents, white pigment, gemstones, radiometric and radioactive dating |
