Glaucophane
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 | |
|---|---|
Bleu Gemm glaucophane with fuchsite | |
| General | |
| Category | Inosilicates Sodic amphibole group |
| Formula (repeating unit) | ☐Na2(Mg3Al2)Si8O22(OH)2 |
| IMA symbol | Gln |
| 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 | |
Glaucophane crystallizes in the monoclinic system.
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