Aegirine
| Aegirine | |
|---|---|
| General | |
| Category | Silicate mineral, pyroxene |
| Formula | NaFe3+[Si2O6] |
| IMA symbol | Aeg |
| Strunz classification | 9.DA.25 |
| Crystal system | Monoclinic |
| Crystal class | Prismatic (2/m) (same H-M symbol) |
| Space group | C2/c |
| Unit cell | a = 9.658, b = 8.795 c = 5.294 [Å], β = 107.42°; Z = 4 |
| Identification | |
| Formula mass | 231.00 g/mol |
| Color | Dark Green, Greenish Black |
| Crystal habit | Prismatic crystals may be in sprays of acicular crystals, fibrous, in radial concretions |
| Twinning | Simple and lamellar twinning common on {100} |
| Cleavage | Good on {110}, (110) ^ (110) ≈87°; parting on {100} |
| Fracture | Uneven |
| Tenacity | Brittle |
| Mohs scale hardness | 6 |
| Luster | Vitreous to slightly resinous |
| Streak | Yellowish-grey |
| Diaphaneity | Translucent to opaque |
| Specific gravity | 3.50–3.60 |
| Optical properties | Biaxial (−) |
| Refractive index | nα = 1.720 – 1.778 nβ = 1.740 – 1.819 nγ = 1.757 – 1.839 |
| Birefringence | δ = 0.037 – 0.061 |
| Pleochroism | X = emerald green, deep green; Y = grass-green, deep green, yellow; Z = brownish green, green, yellowish brown, yellow |
| 2V angle | Measured: 60° to 90°, Calculated: 68° to 84° |
| Dispersion | moderate to strong r > v |
| References | |
Aegirine is a mineral. It is a member of the clinopyroxene group of inosilicate minerals. Acmite is a fibrous green-colored variety of aegirine, with the name also used as a synonym. It was first described in 1821, in Kongsberg, Norway.