Formula: CaV4+5V5+2O16.3H2O
Specific gravity: 2.91 measured, 2.920 calculated for the empirical formula, 2.927 calculated for the ideal formula
Hardness: 2½
Streak: Light greenish blue
Colour: Dark blue
Luminescence: Not fluorescent under UV

Sedimentary environments
Hydrothermal environments

Pandoraite-Ca is a relatively new mineral, approved in 2018 and to date (July 2022) reported only from the type locality.


At the type locality, the Pandora mine, La Sal Mine, La Sal Mining District, San Juan County, Utah, USA, the uranium and vanadium ore mineralisation was deposited where solutions rich in uranium and vanadium encountered pockets of strongly reducing solutions that had developed around accumulations of carbonaceous plant material. Under ambient temperatures and generally oxidising near-surface conditions, water reacts with pyrite and chalcopyrite to form aqueous solutions with relatively low pH (acid), which then react with earlier-formed montroseite-corvusite assemblages, resulting in diverse suites of secondary minerals.
Pandoraite-Ba and pandoraite-Ca are rare and occur on matrix consisting of recrystallized quartz grains from the original sandstone that are intermixed with an unknown iron-vanadium-oxide phase.
Remarkably large and well-formed crystals of finchite are associated with pandoraite-Ca. The pandoraite minerals occur as thin, dark blue, square plates up to approximately 100 microns across and approximately 2 microns thick (CM 57.255-265).

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