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Formula: Na4MgV5+10O28.24H2O
Decavanadate,
pascoite group
Specific gravity: 2.39
Hardness: 2½ to 3
Streak: Yellow
Colour: Yellowish orange to orange
Solubility: Easily soluble in water
Melting point: 500oC
Environments
Sedimentary environments
Hydrothermal environments
Huemulite has been formed after opening copper-uranium deposits in
sandstone and conglomerate;
the vanadium may be derived from associated asphalt. Associated minerals include
hummerite, rossite,
thénardite, gypsum and
epsomite
(HOM).
Localities
At the type locality, the Huemul mine, Pampa Amarilla mining district, Malargüe Department, Mendoza Province, Argentina, the
deposit is sedimentary. Basic volcanic bodies, predominantly hornblendiferous
andesite, cut through the sediments, and there are some small outcrops
of ignimbritic tuff. The uranium ore-bodies are located in
conglomerate and sandstone,
which is always associated with asphalt. It is suggested that the asphalt originates from the oil in the adjacent
oil field of Pampa Amarilla. Uraninite is the principal uranium mineral,
occurring with copper and iron sulfides
such as chalcopyrite, chalcocite,
covellite, bornite,
idaite, pyrite,
marcasite and small amounts of galena and
sphalerite. No primary
vanadium minerals have been found as yet. The probable source of the
vanadium in huemulite is the asphalt. In the alteration zone above the
water-table, many hydrated yellow minerals like tyuyamunite,
sengierite, carnotite,
cuprosklodowskite, autunite,
bayleyite and andersonite are found
in close association with copper minerals such as
malachite, azurite and
chalcanthite.
Huemulite was found the first time in the ore-body Agua Botada, and later in the Huemul and Agua Botada Sur mines.
(AM 51.1-13).
It occurs as fibrous crusts and films, as a post-mining product. Associated minerals include
thénardite, rossite,
quartz, hummerite,
gypsum and epsomite
(Mindat).
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