What is Osarizawaite?
Osarizawaite is a pale yellow lead-aluminium sulfate hydroxide from the oxidised caps of polymetallic ore deposits.
Mineralogy and crystal structure
Reference formula: PbAl3(SO4)2(OH)6. Osarizawaite belongs to the alunite-jarosite structural family, with lead and aluminium occupying characteristic sites. It commonly occurs as coatings rather than large crystals. Osarizawaite is classified with sulfates and has a trigonal crystal system. Typical hardness is 2.5–3 on the Mohs scale and specific gravity is approximately 3.5–3.7.
Colour, lustre and habit
Typical colours include pale yellow, yellow, white, green. The usual massive, crusty, botryoidal habit and earthy, dull, vitreous lustre help describe a specimen, but colour alone is not diagnostic.
Formation and notable localities
Osarizawaite forms in or is associated with supergene alteration of lead- and copper-bearing sulfide veins. Important documented localities include Osarizawa in Japan, Tsumeb in Namibia, Greece, Australia and the United States.
Pale yellow evidence of ore weathering
Osarizawaite is the surface expression of a deep ore system. Its trigonal framework records the movement of acidic, metal-bearing water through a weathered vein.
Collecting and care
Keep dry and avoid dust, acids and abrasive cleaning; treat lead-bearing material as a toxic mineral specimen.
