Metatorbernite

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Metatorbernite
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Green platy crystals on granite
General
CategoryMineral
Chemical formulaCu(UO2)2(PO4)2·8(H2O)
Identification
ColorLight to dark green
Crystal habitFlat plates
Crystal systemTetragonal-dipyramidal
CleavagePerfect
FractureBrittle
Mohs Scale hardness2.5
LusterVitreous, adamantine
Refractive index1.624-1.626
StreakLight green
Specific gravity3.7-3.8
Other CharacteristicsFile:Radioactive.svg Radioactive

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 Tornbern Bergmann. It is especially closely associated with torbernite, but is also found amongside autunite, meta-autunite and uraninite.

File:Metatorbernite with autunite.jpg
Green metatorbernite with yellow autunite deposits on granite

References

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