Charoite
Charoite K(Ca,Na)
2Si
4O
10(OH,F)•H
2O is a rare silicate mineral, first described in 1978. It is named after the Chara River, despite its being 70 km away from the discovery place; the name of the river translated from Evenki means “to melt, melt.” When it was discovered, it was thought to be a fake, dyed purple to give it its striking appearance.
| Charoite | |
|---|---|
| General | |
| Category | Silicate mineral |
| Formula (repeating unit) | K(Ca,Na) 2Si 4O 10(OH,F)•H 2O |
| IMA symbol | Cha |
| Crystal system | Monoclinic |
| Crystal class | Prismatic (2/m) (same H-M symbol) |
| Space group | P21/m |
| Identification | |
| Color | Violet, lilac, light brown |
| Crystal habit | Fibrous, massive |
| Cleavage | Good in three directions |
| Fracture | Conchoidal |
| Mohs scale hardness | 5 - 6 |
| Luster | Vitreous to pearly |
| Streak | White |
| Diaphaneity | Translucent |
| Specific gravity | 2.54 - 2.58 |
| Optical properties | Biaxial (+) |
| Refractive index | nα = 1.550 nβ = 1.553 nγ = 1.559 |
| Birefringence | 0.009 |
| Ultraviolet fluorescence | Weakly fluorescent |
| Common impurities | Al, Fe, Mn, Sr, Ba |
| Other characteristics | Radioactive 10.69% (K) |
| References | |
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