Margaritasite

margaritasite

zircon

uranophane

weeksite

Images

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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