Glaucophane | |
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General | |
Category | Inosilicates Sodic amphibole group |
Formula (repeating unit) | ☐Na2(Mg3Al2)Si8O22(OH)2 |
IMA symbol | Gln[1] |
Strunz classification | 9.DE.25 |
Crystal system | Monoclinic |
Crystal class | Prismatic (2/m) (same H-M symbol) |
Space group | C2/m |
Identification | |
Color | Gray, navy blue, lavender-blue |
Crystal habit | slender long prisms, Massive granular to columnar |
Cleavage | Good on [110] and on [001] |
Fracture | Brittle – conchoidal |
Mohs scale hardness | 6.0–6.5 |
Luster | Vitreous – pearly |
Streak | Grayish blue |
Diaphaneity | Translucent |
Specific gravity | 3–3.15 |
Optical properties | Biaxial (−) |
Refractive index | nα = 1.606 – 1.637 nβ = 1.615 – 1.650 nγ = 1.627 – 1.655 |
Birefringence | δ = 0.021 |
Pleochroism | Strong |
Dispersion | Strong |
References | [2][3][4][5] |
Glaucophane is the name of a mineral and a mineral group belonging to the sodic amphibole supergroup of the double chain inosilicates, with the chemical formula ☐Na2(Mg3Al2)Si8O22(OH)2.
Glaucophane crystallizes in the monoclinic system.