Rocks and Minerals/Identification List
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This page covers information about each of the rocks and minerals on the Rocks and Minerals List, included with the rules.
Rocks
Metamorphic
Amphibolite
| Picture | 
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|---|---|
| Classification | Metamorphic |
| Composition | Amphibole, plagioclase feldspar |
| Environment of Formation | Regional metamorphism of mafic igneous rocks or clay-rich sedimentary rocks |
| Texture | Nonfoliated |
| Economic Importance | Durable building, decorative, crushed aggregate for roads, historically used to produce tools
can include garnet |
| Average Density | 2.9-3.14 |
Gneiss (60)
| Picture | 
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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)
| Picture | 
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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)
| Picture | 
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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)
| Picture | 
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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)
| Picture | 
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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)
| Picture | 
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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)
| Picture | 
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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)
| Picture | 
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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)
| Picture | 
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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)
| Picture | 
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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)
| Picture |  |
|---|---|
| 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)
| Picture | 
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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)
| Picture | 
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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)
| Picture | 
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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)
| Picture | 
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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)
| Picture | 
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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)
| Picture | 
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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 |
Tuff (?)
| Picture | 
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|---|---|
| Classification | Igneous |
| Composition | Felsic (Volcanic Ash, Quartz, Alkali Feldspar, Plagioclase Feldspar) |
| Environment of Formation | Extrusive, Volcanic |
| Texture | Pyroclastic |
| Economic Importance | Architecture, hydraulic cement |
| Average Density | 1.8-2.5 |
Tuff Breccia (?)
| Picture | 
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|---|---|
| Classification | Igneous |
| Composition | Felsic (Quartz, Potassium Feldspar, Plagioclase Feldspar, Biotite, Amphibole) |
| Environment of Formation | Extrusive, Volcanic |
| Texture | Pyroclastic |
| Economic Importance | Construction, fill material |
| Average Density | 2.0-2.7 |
Sedimentary
Arkose (78)
| Picture | 
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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)
| Picture | 
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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)
| Picture | 
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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)
| Picture | 
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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)
| Picture | 
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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)
| Picture | 
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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)
| Picture | 
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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)
| Picture | 
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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)
| Picture | 
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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)
| Picture | 
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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)
| Picture | 
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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)
| Picture | 
|
|---|---|
| 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)
| Picture | 
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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)
| Picture | 
|
|---|---|
| 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)
| Picture | 
|
|---|---|
| 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)
| Picture | 
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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)
| Picture |  |
|---|---|
| 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)
| Picture |  |
|---|---|
| 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)
| Picture |  |
|---|---|
| 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)
| Picture |  |
|---|---|
| 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)
| Picture |  |
|---|---|
| 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)
| Picture |  |
|---|---|
| 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 |
Magnesite
| Picture |  |
|---|---|
| Classification | Carbonates |
| Chemical Composition | MgCO3 |
| Hardness | 3.5-4.5 |
| Streak | White |
| Luster | Vitreous |
| Cleavage | Perfect |
| Fracture | Conchoidal |
| Density | 3- 3.1 g/cm3 |
| Mineral Habit | Normally massive, can be rhombohedral or hexagonal |
| Crystal System | Trigonal |
| Environment of Formation | High temperatures/pressures with water and carbon dioxide, often hydrothermal |
| Economic Importance | Manufacture of cements, steels, and fertilizers, tanning and dyeing, flame retardant |
Native Elements
Copper (16)
| Picture |  |
|---|---|
| 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)
| Picture |  |
|---|---|
| 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)
| Picture |  |
|---|---|
| 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)
| Picture |  |
|---|---|
| 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)
| Picture | _2_(17284861175).jpg) |
|---|---|
| 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. |
Sulfur (54)
| Picture |  |
|---|---|
| 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)
| Picture |  |
|---|---|
| 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)
| Picture |  |
|---|---|
| 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)
| Picture |  |
|---|---|
| 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)
| Picture |  |
|---|---|
| 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)
| Picture |  |
|---|---|
| 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)
| Picture |  |
|---|---|
| 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)
| Picture |  |
|---|---|
| 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)
| Picture |  |
|---|---|
| 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 |
Fluorapatite
| Picture | .jpg) |
|---|---|
| Classification | Phosphate group |
| Chemical Composition | Ca5(PO4)3F |
| Hardness | 5 |
| Streak | White |
| Luster | Vitreous |
| Cleavage | Indiscernible |
| Fracture | Brittle to conchoidal |
| Density | 3.1 - 3.2 g/cm3 |
| Mineral Habit | Massive to prismatic crystalline |
| Crystal System | Hexagonal |
| Environment of Formation | Common in magnetite deposits and hydrothermal veins, occurs in almost all igneous rocks |
| Economic Importance | Source of phosphorus in fertilizers, chemical manufacturing, toothpaste and bone repair |
Sulfates
Barite (9)
| Picture |  |
|---|---|
| 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)
| Picture |  |
|---|---|
| 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)
| Picture |  |
|---|---|
| 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)
| Picture |  |
|---|---|
| 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)
| Picture |  |
|---|---|
| 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 |