White crystals of the extremely rare aluminium mineral riotintoite from the type and only known locality worldwide: La Vendida Mine, Sierra Gorda, Antofagasta Region, Chile. — Photo: David Hospital · CC BY-SA 4.0
Riotintoite
Riotintoite is an IMA-recognized mineral species in the sulfate class, with the chemical formula Al(SO₄)(OH)·3H₂O.
It crystallizes in the triclinic crystal system (space group P-1).
Key properties: Mohs hardness 2.5; specific gravity 2.13; Vitreous luster; optically biaxial.
IMA symbol Rio, IMA status: approved, named in 2015.
Found as a secondary mineral in fissures cutting highly-altered volcanic breccia.
It is found associated with Vendidaite, eriochalcite, Mg-rich aubertite, magnesioaubertite, belloite, alunite, kaolinite, halloysite.
The name refers to the former (before 1990) name of the mine, Rio Tinto, that produced the first samples.