What is Petalite?
Petalite is a light lithium aluminium silicate valued as a pale gemstone and as an important lithium mineral in granitic pegmatites.
Mineralogy and crystal structure
Reference formula: LiAlSi4O10. Petalite is monoclinic and commonly cleaves strongly. Transparent material may be faceted, while pegmatite crystals reveal its role in lithium-rich magmatic evolution. Petalite is classified with silicates and has a monoclinic crystal system. Typical hardness is 6–6.5 on the Mohs scale and specific gravity is approximately 2.4–2.5.
Colour, lustre and habit
Typical colours include colourless, white, grey, pink. The usual tabular, prismatic, massive habit and vitreous, pearly lustre help describe a specimen, but colour alone is not diagnostic.
Formation and notable localities
Petalite forms in or is associated with lithium-rich granitic pegmatites and late-stage cavities. Important documented localities include Brazil, Zimbabwe, Sweden, Madagascar, Namibia and the United States.
A clear lithium pegmatite gemstone
Petalite is commercially interesting because one pale, elegant mineral links fine jewellery with the evolution of lithium-bearing pegmatites.
Collecting and care
Handle edges carefully, avoid strong impact and clean with mild soap and water.
