What is Woodhouseite?
Woodhouseite is a hydrated calcium aluminium phosphate sulfate, usually pale and associated with altered phosphate-rich pegmatites and hydrothermal zones.
Mineralogy and structure
Reference formula: CaAl3(PO4)(SO4)(OH)6. Woodhouseite is trigonal and belongs to the alunite supergroup. COD 9000033 provides an exact Ca-bearing structural reference; natural substitutions toward svanbergite are possible. Woodhouseite is classified with phosphates and has trigonal crystal symmetry. Typical hardness is 3.5–4 on the Mohs scale and specific gravity is approximately 2.7–2.9.
Colour, lustre and habit
Typical colours include colourless, white, cream, pale yellow, brownish. The usual rhombohedral, granular, crusty habit and vitreous, pearly, dull lustre help describe a specimen, but colour alone is not diagnostic.
Formation and notable localities
Woodhouseite forms in or is associated with altered granite pegmatites, phosphate-rich cavities, hydrothermal veins and aluminium-rich weathering zones. Important documented localities include Brazil, the United States, Germany, Portugal and Australia.
A pale phosphate-sulfate from an altered pegmatite
Woodhouseite rewards close inspection: its understated colour and alunite-group structure are most attractive when the specimen comes with a clear alteration and locality story.
Collecting and care
Protect from acids, abrasion and prolonged moisture; preserve the pegmatite or phosphate association.
