Lepidolite
Lepidolite is a lilac-gray or rose-colored member of the mica group of minerals with chemical formula K(Li,Al)3(Al,Si,Rb)4O10(F,OH)2. It is the most abundant lithium-bearing mineral and is a secondary source of this metal. It is the major source of the alkali metal rubidium.
| Lepidolite | |
|---|---|
| General | |
| Category | Phyllosilicate |
| Formula (repeating unit) | K(Li,Al)3(Al,Si,Rb)4O10(F,OH)2 |
| IMA symbol | Lpd |
| Strunz classification | 9.EC.20 |
| Crystal system | Monoclinic |
| Crystal class | Prismatic (2/m) (same H-M symbol) |
| Space group | C2/m, Cm |
| Unit cell | a = 5.209(2) Å, b = 9.011(5) Å, c = 10.149(5) Å; β = 100:77(4)°; Z = 2 |
| Identification | |
| Color | Pink, light purple, purple, rose-red, violet-gray, yellowish, white, colorless other colors possible but are rare. |
| Crystal habit | Tabular to prismatic pseudohexagonal crystals, scaly aggregates and massive |
| Twinning | Rare, composition plane {001} |
| Cleavage | {001} perfect |
| Fracture | Uneven |
| Mohs scale hardness | 2.5–3 |
| Luster | Vitreous to pearly |
| Streak | White |
| Diaphaneity | Transparent to translucent |
| Specific gravity | 2.8–2.9 |
| Optical properties | Biaxial (−) |
| Refractive index | nα=1.525–1.548, nβ=1.551–1.58, nγ=1.554–1.586 |
| Birefringence | 0.0290–0.0380 |
| Pleochroism | X = almost colorless; Y = Z = pink, pale violet |
| 2V angle | 0° – 58° measured |
| References | |
Lepidolite is found with other lithium-bearing minerals, such as spodumene, in pegmatite bodies. It has also been found in high-temperature quartz veins, greisens and granite.
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