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Formula: Cs2(UO2)2(VO4)2.H2O
Hydrated normal uranyl vanadate,
carnotite group, cesium-bearing mineral
Crystal System: Monoclinic
Specific gravity: 5.41 calculated
Hardness: 2
Streak: Light yellow
Colour: Yellow
Luminescence: Not fluorescent under UV
RADIOACTIVE
Environments
Volcanic igneous environments
Hydrothermal environments
Although margaritasite was approved in 1980, to date (October 2022) it has been reported only from the
type localities.
Localities
There are two co-type localities, the Margaritas No. 1 and No. 2 mines, Sierra Peña Blanca, Peña Blanca District, Aldama
Municipality, Chihuahua, Mexico. Here margaritasite occurs as fine-grained yellow aggregates up to 1 mm of
individual crystals 1 to 3 µm in size in fumarole deposits in rhyolite,
and as pore fillings and phenocryst casts in felsic volcanic
tuffs, which have been altered by high-temperature hydrothermal fluids.
Associated minerals include zircon,
sanidine, quartz,
pyrite, kaolinite and
apatite
(Mindat, HOM).
Other uranium ore minerals found in the Margaritas deposit include uranophane,
autunite and
weeksite; they all contain hexavalent uranium and are associated with
anomalously high concentrations of molybdenum (probably in
powellite) and vanadium in
metatyuyamunite as well as in margaritasite. No tetravalent
uranium minerals have been observed in the deposit
(AM 67.1273-1289).
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