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Formula: Mg(VO3)2.8H2O
Hydrated vanadate
Crystal System: Triclinic
Specific gravity: 1.97 measured, 1.974 calculated
Hardness: Probably ~2
Streak: White
Colour: Light tan
Luminescence: Nonfluorescent
Solubility: Soluble in water at room temperature
Environments
Sedimentary environments
Hydrothermal environments
Pseudodickthomssenite is a new mineral, approved in 2021 and to date (October 2022) reported only from the type
locality.
Localities
The type locality, Pickett Corral No. 4, Uravan Mining District, Montrose County, Colorado, USA, lies in a mineral belt
that contains deposits in sandstones. The deposition of the uranium and
vanadium ores occurred where solutions containing these elements came into
contact with strongly reducing conditions associated with carbonaceous plant material. Pseudodickthomssenite was
found underground in the Pickett Corral mine in partially flooded workings. It was found in one small area on only one
micromount specimen. It occurs on asphaltite and
montroseite- and corvusite-
bearing sandstone. Other
secondary minerals occurring on the same micromount are
dickthomssenite, gypsum,
huemulite, lasalite and
trebiskyite. Pseudodickthomssenite forms from the oxidation of
montroseite-corvusite assemblages
in a moist environment. Mining operations have exposed unoxidised and oxidised phases. Under ambient temperatures and
generally oxidising near-surface conditions, water reacts with pyrite to form
aqueous solutions with relatively low pH (acid). The various
secondary vanadate
phases that form depend upon prevailing Eh-pH conditions and the presence of other cations.
Pseudodickthomssenite occurs in one diverging cluster of striated needles up to about 500 microns long and 20
microns in diameter
(CM 60.797-804).
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