Outstanding orange crystals of hummerite, a very rare K-Mg vanadium oxide, on a contrasting matrix. From: Lichtenberg Absetzer Dump, Ronneburg, Thuringia, Germany. — Photo: David Hospital · CC BY-SA 4.0
Hummerite
Hummerite is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula KMgV⁵⁺₅O₁₄·8H₂O.
It crystallizes in the triclinic crystal system (space group P-1). It is a member of the Pascoite structural group.
Key properties: specific gravity 2.53; optically biaxial.
IMA symbol Hum, grandfathered status — known before the IMA’s founding, named in 1951.
Leached from vanadium oxide ores and deposited in veins in clay and as efflorescences on bedded or roll-front U-V deposits in sandstone.
It is found associated with Huemulite, rossite, thenardite, gypsum, epsomite (Malargüe district, Argentina); gypsum, huemulite, metamunirite, munirite, bluestreakite (Blue Streak mine.
The name refers to the Hummer mine, Colorado, USA, where it occurs.