Decavanadate, member of the pascoite family
Specific gravity: 2.29 calculated
Colour: Orange to golden orange
Solubility: highly soluble in water, acetone and alcohol
Hughesite can be unstable in very arid environments, leading to partial dehydration
At the type locality, the West Sunday Mine, Slick Rock Mining District, San Miguel County, Colorado, USA, orange to golden orange crystals of hughesite occur in efflorescent crusts, averaging 2 mm thick, on the sandstone walls of mine workings and in rock fractures. Hughesite forms through the oxidation of corvusite and montroseite, the primary vanadium oxide phases present, as they react with acidic, oxidising groundwater in uranium-vanadium deposits, usually in organic-carbon-rich zones. Secondary mineralisation occurs during evaporation of the groundwater, leaving a crust of hughesite and other oxidised vanadium minerals on rock surfaces. Associated minerals include rossite, lasalite, hewettite, sherwoodite, corvusite, montroseite, rakovanite and gunterite (CM 49.1253-1265, HOM).
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