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Formula: CaV4+5V5+2O16.3H2O
Vanadate
Crystal System: Monoclinic
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
Environments
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.
Localities
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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