Rossite. Field of view 7 mm. From: Arrowhead tunnel, Bull Pen Canyon, San Miguel Co., Colorado, USA. — Photo: Leon Hupperichs · CC BY-SA 3.0
Rossite
Rossite is an IMA-recognized mineral species in the vanadate class, with the chemical formula Ca(VO₃)₂·4H₂O.
It crystallizes in the triclinic crystal system (space group P-1).
Key properties: Mohs hardness 2–3; specific gravity 2.45; Vitreous to somewhat pearly luster; optically biaxial.
IMA symbol Rs, grandfathered status — known before the IMA’s founding, named in 1927.
Found in veinlets in carnotite-bearing sandstone (Bull Pen Canyon, Colorado, USA).
It is found associated with Metarossite, carnotite, gypsum (Bull Pen Canyon, Colorado, USA); huemulite, hummerite, thenardite, gypsum, epsomite (Malargüe district, Argentina).
The mineral was named to honor Dr. Clarence Samuel Ross (1880–1975), American geologist and mineralogist, U.S. Geological Survey, Washington, D.C., USA.