What is Pollucite?
Pollucite is a rare caesium-rich zeolite-group mineral from evolved granitic pegmatites, usually pale and valued for its unusual chemistry.
Mineralogy and crystal structure
Reference formula: CsAlSi2O6·H2O. Pollucite has a cubic zeolite framework with channels that host caesium and water. Composition and hydration vary, but the mineral is a valuable indicator of extremely evolved pegmatite fluids. Pollucite is classified with silicates and has a cubic crystal system. Typical hardness is 6.5–7 on the Mohs scale and specific gravity is approximately 2.8–3.0.
Colour, lustre and habit
Typical colours include colourless, white, grey, pink. The usual cubic, massive, granular habit and vitreous lustre help describe a specimen, but colour alone is not diagnostic.
Formation and notable localities
Pollucite forms in or is associated with highly fractionated lithium-caesium-tantalum pegmatites. Important documented localities include Canada, Myanmar, Zimbabwe, Afghanistan, Brazil and the United States.
A pale crystal recording pegmatite evolution
Pollucite is understated in colour but exceptional in chemistry: its framework marks the final, caesium-rich stages of a highly evolved granite melt.
Collecting and care
Protect from impact and acids; retain matrix and locality because pale pollucite can resemble common feldspar.
