Epidote
Epidote is a calcium aluminium iron sorosilicate mineral.
| Epidote | |
|---|---|
Epidote crystals | |
| General | |
| Category | Sorosilicates |
| Formula (repeating unit) | {Ca2}{Al2Fe3+}(SiO4)(Si2O7)O(OH) |
| IMA symbol | Ep |
| Crystal system | Monoclinic |
| Crystal class | Prismatic (2/m) (same H-M symbol) |
| Space group | P21/m |
| Identification | |
| Color | Pistachio-green, yellow-green, greenish black, brownish-green, green, black |
| Crystal habit | Prismatic with striations, fibrous, massive |
| Twinning | On [100] |
| Cleavage | {001} perfect and {100} imperfect |
| Fracture | Flat regular to uneven |
| Mohs scale hardness | 6–7 |
| Luster | Vitreous to resinous |
| Streak | Greyish white |
| Diaphaneity | Transparent to nearly opaque |
| Specific gravity | 3.38–3.49 |
| Optical properties | Biaxial (-) |
| Refractive index | nα = 1.715–1.751 nβ = 1.725–1.784 nγ = 1.734–1.797 |
| Birefringence | δ = 0.019–0.046 |
| Pleochroism | Strong |
| References | |
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