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Formula: (NH4)(UO2)(AsO4).3H2O
Hydrated uranyl arsenate,
meta-autunite group
Crystal system: Tetragonal
Specific gravity: 3.22 measured, 3.286 calculated
Hardness: 2½
Colour: Light green
Luminescence: Fluoresces green under UV, as is typical of the uranyl ion
Solubility:
Common impurities: Ammonium may be replaced by minor hydronium (H3O)1+, and As by minor P
(Mindat).
RADIOACTIVE
Environments
Localities
At the type locality, Bota-Burum U deposit, Alakol District, Jetisu Region, Kazakhstan, uramarsite was
discovered in the supergene zone of the deposit. It is a
phase that formed by oxidation of pitchblende-sulphide mineralisation in highly fractured zones in
hydrothermally altered porphyritic rocks. It is associated with
calcite, arsenopyrite,
pyrite, galena,
chistyakovaite,
natrouranospinite,
scorodite,
arseniosiderite,
mansfieldite,
metazeunerite and
trögerite. Uramarsite and
chistyakovaite form blocky pseudocrystals with sharp orthogonal
boundaries between the two phases.
Uramarsite forms imperfect, platy crystallites to 2 mm in size, films, and, less often, flattened square
crystals to 0.1 mm in size
(AM 94.2.405).
Uramarsite from Bota-Burum U deposit -
Image
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