Chemistry:Metatorbernite

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Metatorbernite
Torbernite-Metatorbernite-Curite-201043.jpg
General
CategoryPhosphate minerals
Formula
(repeating unit)
Cu(UO2)2(PO4)2·8(H2O)
Strunz classification8.EB.10
Crystal systemTetragonal
Crystal classDipyramidal (4/m)
(same H-M symbol)
Space groupP4/n
Identification
ColourLight to dark green
Crystal habitFlat plates
CleavagePerfect
FractureBrittle
Mohs scale hardness2.5
Vitreous, adamantine|re|er}}Vitreous, adamantine
StreakLight green
Specific gravity3.7–3.8
Refractive index1.624–1.626
Other characteristicsRadioactive.svg Radioactive
References[1][2][3]

Metatorbernite (or meta-torbernite) is a radioactive phosphate mineral, and is a dehydration pseudomorph of torbernite. Chemically, it is a copper uranyl phosphate and usually occurs in the form of green platy deposits. It can form by direct deposition from a supersaturated solution, which produces true crystalline metatorbernite, with a dark green colour, translucent diaphaneity, and vitreous lustre. However, more commonly, it is formed by the dehydration of torbernite, which causes internal stress and breakage within the crystal lattice, resulting in crystals composed of microscopic powder held together using electrostatic force, and having a lighter green colour, opaque diaphaneity, and a relatively dull lustre. As with torbernite, it is named after the Swedish chemist Torbern Bergman. It is especially closely associated with torbernite, but is also found amongside autunite, meta-autunite and uraninite.

References

Metatorbernite from the Margabal Mine, Entraygues-sur-Truyère, France. Size: 4 x 3 x 1.8 cm.