Coesite | |
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General | |
Category | Tectosilicate, quartz group |
Formula (repeating unit) | SiO2 |
IMA symbol | Coe[1] |
Strunz classification | 4.DA.35 |
Crystal system | Monoclinic |
Crystal class | Prismatic (2/m) (same H–M symbol) |
Space group | C2/c |
Unit cell | a = 7.143 b = 12.383 c = 7.143 [Å] β = 120.00° Z = 16 |
Identification | |
Formula mass | 60.0843 g/mol |
Color | Colorless |
Crystal habit | Inclusions in UHP metamorphic minerals up to 3 mm in size |
Fracture | Conchoidal |
Tenacity | Brittle |
Mohs scale hardness | 7.5-8 |
Luster | Vitreous |
Streak | White |
Diaphaneity | Transparent |
Density | 2.92 (calculated) |
Optical properties | Biaxial |
Refractive index | nx = 1.594 ny = 1.595 nz = 1.599 |
Birefringence | +0.006 |
2V angle | 60–70 |
References | [2] |
Coesite (/ˈkoʊsaɪt/)[3] is a form (polymorph) of silicon dioxide (SiO2) that is formed when very high pressure (2–3 gigapascals), and moderately high temperature (700 °C, 1,300 °F), are applied to quartz. Coesite was first synthesized by Loring Coes, Jr., a chemist at the Norton Company, in 1953.[4][5]