What is Ximengite?
Ximengite is a colourless to white bismuth phosphate from altered tin deposits, a trigonal mineral with a distinctive heavy-element chemistry.
Mineralogy and structure
Reference formula: BiPO4. Ximengite is trigonal with the ideal formula BiPO4. COD 9008088 provides an exact structural reference; synthetic polymorphs of BiPO4 are known, so the natural trigonal phase is specified. Ximengite is classified with phosphates and has trigonal crystal symmetry. Typical hardness is 4–5 on the Mohs scale and specific gravity is approximately 5.4–5.6.
Colour, lustre and habit
Typical colours include colourless, white, pale grey. The usual granular, massive, crusty habit and vitreous, greasy lustre help describe a specimen, but colour alone is not diagnostic.
Formation and notable localities
Ximengite forms in or is associated with altered tin deposits, bismuthinite-bearing hydrothermal veins and phosphate-rich secondary assemblages. Important documented localities include the Amo tin deposit in Yunnan, China, Italy, the Democratic Republic of the Congo and other bismuth districts.
A quiet white mineral with heavy-element chemistry
Ximengite is a good example of how an understated colour can hide a dense bismuth-rich composition. Its value rises with clear locality and association information.
Collecting and care
Protect from impact and acids; keep away from dust and retain the tin-ore association and locality.
