Formula: Ca2MgV5+10O28.16H2O
Vanadium oxysalt, pascoite group
Specific gravity: 2.43
Hardness: 2½
Streak: Yellow
Colour: Bright orange

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).


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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