Petalite

phyllosilicate

pegmatite

Formula: LiAlSi4O10
Phyllosilicate (sheet silicate), feldspathoid
Specific gravity: 2.3 to 2.5
Hardness: 6 to 6½
Streak: White
Colour: Colourless, white, grey, pink
Solubility: Insoluble in acids
Environments:

Pegmatites

Petalite is found in granite pegmatites and related rocks, associated with spodumene, tourmaline, lepidolite, topaz, microcline, amblygonite, apatite, pollucite, columbite, cleavelandite and quartz.

Alteration

Petalite alters to montmorillonite.

petalite to spodumene and quartz
LiAlSi4O10 ⇌ LiAlSi2O6 + 2SiO2

Common impurities: Mg,Fe,Na,Ca,K,H2O

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