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A mineral is a naturally occurring chemical compound, usually of crystalline form and abiogenic in origin. A mineral has one specific chemical composition, whereas a rock can be an aggregate of different minerals or mineraloids. The study of minerals is called mineralogy.

There are over 5,300 known mineral species; over 5,070 of these have been approved by the International Mineralogical Association (IMA). The silicate minerals compose over 90% of the Earth's crust. The diversity and abundance of mineral species is controlled by the Earth's chemistry. Silicon and oxygen constitute approximately 75% of the Earth's crust, which translates directly into the predominance of silicate minerals.

Minerals are distinguished by various chemical and physical properties. Differences in chemical composition and crystal structure distinguish the various species, which were determined by the mineral's geological environment when formed. Changes in the temperature, pressure, or bulk composition of a rock mass cause changes in its minerals.

Minerals can be described by their various physical properties, which are related to their chemical structure and composition. Common distinguishing characteristics include crystal structure and habit, hardness, lustre, diaphaneity, colour, streak, tenacity, cleavage, fracture, parting, and specific gravity. More specific tests for describing minerals include magnetism, taste or smell, radioactivity and reaction to acid.

Crystal family Lengths Angles Common examples
Isometric a=b=c α=β=γ=90° Garnet, halite, pyrite
Tetragonal a=b≠c α=β=γ=90° Rutile, zircon, andalusite
Orthorhombic a≠b≠c α=β=γ=90° Olivine, aragonite, orthopyroxenes
Hexagonal a=b≠c α=β=90°, γ=120° Quartz, calcite, tourmaline
Monoclinic a≠b≠c α=γ=90°, β≠90° Clinopyroxenes, orthoclase, gypsum
Triclinic a≠b≠c α≠β≠γ≠90° Anorthite, albite, kyanite
Mohs hardness Mineral Chemical formula
1 Talc Mg3Si4O10(OH)2
2 Gypsum CaSO4·2H2O
3 Calcite CaCO3
4 Fluorite CaF2
5 Apatite Ca5(PO4)3(OH,Cl,F)
6 Orthoclase KAlSi3O8
7 Quartz SiO2
8 Topaz Al2SiO4(OH,F)2
9 Corundum Al2O3
10 Diamond C

2 KAlSi3O8 + 5 H2O + 2 H+ → Al2Si2O5(OH)4 + 4 H2SiO3 + 2 K+
Al2Si2O5(OH)4 + SiO2 → Al2Si4O10(OH)2 + H2O
Al2Si4O10(OH)2 → Al2SiO5 + 3 SiO2 + H2O
  • Busbey, A.B.; Coenraads, R.E.; Roots, D.; Willis, P. (2007). Rocks and Fossils. San Francisco: Fog City Press. ISBN . 
  • Chesterman, C.W.; Lowe, K.E. (2008). Field guide to North American rocks and minerals. Toronto: Random House of Canada. ISBN . 
  • Dyar, M.D.; Gunter, M.E. (2008). Mineralogy and Optical Mineralogy. Chantilly, Virginia: Mineralogical Society of America. ISBN . 


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