|
Trilithionite |
Chemical Formula |
KLi2Al(Al,Si)3O10(F,OH)2 |
Species |
Silicates |
Crystal System |
Monoclinic |
Mohs Scale |
2.5-3 |
Specific Gravity |
2.8-2.9 |
Color |
Pink, purple, rose-red, Purple-gray, yellowish, white, colorless |
Streak |
White |
Luster |
Vitreous to pearly |
Refractive Index |
nα=1.525–1.548, nβ=1.551–1.58, nγ=1.554–1.586 |
Diaphaneity |
Transparent to translucent |
Cleavage |
perfect |
Fracture |
Uneven |
Crystal Habit:Tabular to prismatic pseudohexagonal crystals, scaly aggregates and massive |
Lepidolite (KLi
2Al(Al,Si)
3O
10(F,OH)
2 is a lilac-gray or rose-colored polylithionite-trilithionite series, a phyllosilicate mineral series of the mica group that is a secondary source of lithium. It is associated with other lithium-bearing minerals like spodumene in pegmatite bodies. It is one of the major sources of the rare alkali metals rubidium and caesium. In 1861 Robert Bunsen and Gustav Kirchhoff extracted 150 kg of lepidolite and yielded a few grams of rubidium salts for analysis, and therefore discovered the new element rubidium.
It occurs in granite pegmatites, in some high-temperature quartz veins, greisens and granites. Associated minerals include quartz, feldspar, spodumene, amblygonite, tourmaline, columbite, cassiterite, topaz and beryl.
Notable occurrences include Brazil; Ural Mountains, Russia; California, United States; Tanco Mine, Bernic Lake, Manitoba, Canada; and Madagascar.