Actinolite
Actinolite is an amphibole silicate mineral with the chemical formula Ca2(Mg4.5–2.5Fe2+0.5–2.5)Si8O22(OH)2.
| Actinolite | |
|---|---|
Actinolite crystal from Portugal | |
| General | |
| Category | Inosilicates |
| Formula (repeating unit) | Ca2(Mg4.5-2.5Fe2+0.5-2.5) Si8O22(OH)2 |
| IMA symbol | Act |
| Strunz classification | 9.DE.10 |
| Crystal system | Monoclinic |
| Crystal class | Prismatic (2/m) (same H-M symbol) |
| Space group | C2/m |
| Identification | |
| Color | pale to dark green, yellowish green, blue and black. White or grey when in asbestos |
| Crystal habit | bladed, fibrous, radial |
| Twinning | simple or lamellar |
| Cleavage | perfect along {110}. |
| Fracture | uneven |
| Mohs scale hardness | 5–6 |
| Luster | vitreous to dull |
| Streak | white |
| Diaphaneity | translucent to transparent |
| Specific gravity | 3.00 (+0.10, -0.05) |
| Polish luster | vitreous |
| Optical properties | Biaxial (−) |
| Refractive index | nα = 1.613–1.628 nβ = 1.627–1.644 nγ = 1.638–1.655 |
| Birefringence | 0.0250–0.0270 |
| Pleochroism | moderate, yellow to dark green (in stones that are transparent) |
| 2V angle | 78–82° (calc), 84–73° (meas) |
| Dispersion | r < v |
| Ultraviolet fluorescence | inert |
| Absorption spectra | faint line at 503 nm |
| References | |
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