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Formula: Ca2MgV5+10O28.16H2O
Decavanadate,
pascoite group
Crystal System: Monoclinic
Specific gravity: 2.43
Hardness: 2½
Streak: Yellow
Colour: Bright orange
Environments
Sedimentary environments
Hydrothermal environments
Magnesiopascoite is a product of groundwater leaching and oxidation of vanadium oxides in a post-mining
environment. Associated minerals include gypsum,
rossite, pyrite,
montroseite and martyite
(HOM).
Localities
At the type locality, the Blue Cap mine, La Sal Creek Mining District, San Juan County, Utah, USA,
magnesiopascoite was discovered in association with gypsum,
rossite, pyrite,
montroseite and martyite on a
vanadium-uranium oxide-replacement assemblage developed at the expense of
organic material. Other minerals identified from the mine are brochantite,
calcite, coffinite,
corvusite, devilline,
dickthomssenite, dolomite,
lasalite, montroseite,
navajoite, sherwoodite,
uraninite, uranopilite and
zeunerite. Magnesiopascoite was also identified on a sample collected
at the nearby Vanadium Queen mine.
Uranium–vanadium mineralisation in the mines of the area occurs in certain
layers of the sandstone. Carbonaceous material in these layers is
considered to have created a reducing environment that caused the precipitation of uranium and
vanadium oxides, such as uraninite,
corvusite and montroseite, from
solution. Martyite, magnesiopascoite and
rossite appear to have formed from post-mining leaching and oxidation of
vanadium oxides by circulating groundwater.
The magnesiopascoite forms as parallel stackings of lustrous, transparent, bright orange crystals that vary in
aspect from tabular to equant to prismatic
(CM 46.679-686).
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