Phosphosiderite , Barbosalite Locality: Bull Moose Mine, Custer , Custer District, Custer County, South Dakota , USA ( Locality at mindat.org ) Size: 5.0 x 4.0 x 3.5 cm. Sharp, gemmy, transparent crystals of the rare species phosphosiderite, to 1 mm or so, perched on 3-dimensional dark phosphate matrix with black microcrystals of barbosalite. From old finds here (ex. Dr. David Garske). — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Barbosalite
Barbosalite is an IMA-recognized mineral species in the phosphate class, with the chemical formula Fe²⁺Fe³⁺₂(PO₄)₂(OH)₂.
It crystallizes in the monoclinic crystal system (space group P2_1/c). It is a member of the Lazulite structural group.
Key properties: Mohs hardness 6; specific gravity 3.6–3.62; Dark blue streak; Vitreous to earthy luster; optically biaxial.
IMA symbol Bsa, grandfathered status — known before the IMA’s founding, named in 1954.
Found in complex granitic pegmatites, formed by oxidation and hydration of primary phosphates.
It is found associated with Tavorite, huréaulite, heterosite, triphylite, vivianite, roscherite, rockbridgeite.
The mineral was named to honor Aluizio Licinio de Miranda Barbosa (1916–), Professor of Geology, School of Mines, Ouro Preto, Brazil.