Montroseite Locality: Prachovice, Pardubice Region, Bohemia (Böhmen; Boehmen), Czech Republic Black shiny Montroseite crystals from Prachovice. Specimen size 6x4cm. Specimen and photo Leon Hupperichs. — Photo: Leon Hupperichs · CC BY-SA 3.0
Montroseite
Montroseite is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula (V³⁺,Fe²⁺,V⁴⁺)O(OH).
It crystallizes in the orthorhombic crystal system (space group Pbnm). It is a member of the Diaspore structural group.
Key properties: specific gravity 4; Black streak; Submetallic luster.
IMA symbol Mto, grandfathered status — known before the IMA’s founding, named in 1953.
Found in relatively unoxidized Colorado Plateau-type U–V ores in sandstones; thought to be a primary mineral (Colorado, Utah, and Arizona, USA); in vanadiferous anthraxolite bitumen (Guangxi, China).
It is found associated with Paramontroseite, uraninite, corvusite, hewettite, melanovanadite, pascoite, hummerite, pyrite, galena, barite, quartz.
The name refers to Montrose Co., Colorado, USA, where it was first found.