noun
MineralogyA mineral that is a monoclinic hydrated sulphate of aluminium and magnesium, MgAl₂ (SO₄)₄.22H₂ O, occurring as transparent or translucent, usually whitish, aggregates of fibrous or acicular crystals.
Origin
Mid 19th century. From the name of John Pickering, American philologist + -ite.
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