Enstatite
Pyroxene: magnesium-iron silicate with MgSiO3 and FeSiO3 end-members / From Wikipedia, the free encyclopedia
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For E-type chondrites, see Enstatite chondrite.
Enstatite is a mineral; the magnesium endmember of the pyroxene silicate mineral series enstatite (MgSiO3) – ferrosilite (FeSiO3). The magnesium rich members of the solid solution series are common rock-forming minerals found in igneous and metamorphic rocks. The intermediate composition, (Mg,Fe)SiO
3, has historically been known as hypersthene, although this name has been formally abandoned and replaced by orthopyroxene. When determined petrographically or chemically the composition is given as relative proportions of enstatite (En) and ferrosilite (Fs) (e.g., En80Fs20).
Quick Facts General, Category ...
Enstatite | |
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General | |
Category | Inosilicate |
Formula (repeating unit) | MgSiO3 |
IMA symbol | En[1] |
Strunz classification | 9.DA.05 |
Crystal system | Orthorhombic |
Crystal class | Dipyramidal (mmm) H-M symbol: (2/m 2/m 2/m) |
Space group | Pbca |
Unit cell | a = 18.23, b = 8.84 c = 5.19 [Å]; Z = 8 |
Identification | |
Formula mass | 100.387 g·mol−1 |
Color | White, grey, green, yellow or brown - colorless in thin section. |
Crystal habit | Prismatic crystals, commonly lamellar, fibrous, or massive |
Twinning | Simple and lamellar on [100] |
Cleavage | Good/distinct on [210] |
Fracture | Uneven |
Tenacity | Brittle |
Mohs scale hardness | 5 to 6 |
Luster | Vitreous, pearly on cleavage |
Streak | Gray |
Diaphaneity | Translucent to opaque |
Specific gravity | 3.2–3.3 |
Optical properties | Biaxial (+) |
Refractive index | nα = 1.650–1.668; nβ = 1.652–1.673; nγ = 1.659–1.679 |
Birefringence | δ = 0.009–0.011 |
Pleochroism | Pink to green pleochroism diagnostic for enstatite, pale green to pale orange perpendicular to pink-green axis |
2V angle | 55–90° |
References | [2][3][4] |
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