Lepidolite

Lepidolite (floater crystal) Virgem de Lapa, Minas Gerais, Brazil Thumbnail, 2.4 x 2.1 x 0.7 cm © irocks
Chemical Formula: K(Li,Al,Rb)3(Al,Si)4O10(F,OH)2
Locality: Pala, San Diego Co., California, USA.
Name Origin: From the Greek lepidion – “scale” and lithos – “stone.”Lepidolite is a lilac-gray or rose-colored member of the mica group with formula  K(Li,Al,Rb)3(Al,Si)4O10(F,OH)2. It is a secondary source of lithium. It is a phyllosilicate mineral and a member of the polylithionite-trilithionite series.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.

History

Discovery date : 1792
Town of Origin : ROZNA, BYSTRICE, MORAVIE
Country of Origin : TCHEQUIE

Optical properties

Optical and misc. Properties : Translucent
Refractive Index : from 1,52 to 1,58
Axial angle 2V : 0-58°

Physical Properties

Cleavage: {001} Perfect
Color: Colorless, Gray white, Lilac, Yellowish, White.
Density: 2.8 – 2.9, Average = 2.84
Diaphaneity: Translucent
Fracture: Uneven – Flat surfaces (not cleavage) fractured in an uneven pattern.
Hardness: 2.5-3 – Finger Nail-Calcite
Luminescence: Non-fluorescent.
Luster: Vitreous – Pearly
Streak: white

 Photos:

Lepidolite Itinga, Minas Gerais, Brazil Cabinet, 18.5 x 15.1 x 12.5 cm © irocks
Lepidolite Little Three Mine, Ramona, San Diego Co., California, USA Miniature, 5 x 4 x 3.5 cm © irocks
Himalaya Mine (Himalaya dikes; Himalaya pegmatite), Gem Hill, Mesa Grande District, San Diego Co., California, USA © Eric Graff
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