Allier, Les Montmins France — Photo: Pacific Museum of Earth from Canada · CC BY-SA 2.0
Gorceixite
Gorceixite is an IMA-recognized mineral species in the phosphate class, with the chemical formula BaAl₃(PO₄)(PO₃OH)(OH)₆.
It crystallizes in the hexagonal crystal system (space group R3m). It is a member of the Alunite-crandallite structural group.
Key properties: Mohs hardness 6; specific gravity 3.04–3.19; Vitreous luster; optically uniaxial.
IMA symbol Gcx, grandfathered status — known before the IMA’s founding, named in 1906.
Probably always a secondary mineral; in novaculites and other sedimentary rocks; in carbonatites; from hydrothermal argillic alteration zones; in topaz greisen; in the fine-grained fraction of soils.
It is found associated with Dawsonite, alumohydrocalcite, nordstrandite (Sydney Basin, Australia); lazulite, siderite, “limonite”, quartz (Big Fish River, Canada); diamond (river sands.
The mineral was named to honor Henrique Gorceix (1842-1919), French mining geologist and mineralogist, Director, School of Mines, Ouro Preto, Brazil.