Metatorbernite

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Metatorbernite
Metatorbernite.jpg
Green platy crystals on granite. Specimen from Redruth, Cornwall, UK
General
Category Phosphate minerals
Formula
(repeating unit)
Cu(UO2)2(PO4)2·8(H2O)
Strunz classification 08.EB.10
Identification
Color Light to dark green
Crystal habit Flat plates
Crystal system Tetragonal-dipyramidal
Cleavage Perfect
Fracture Brittle
Mohs scale hardness 2.5
Luster Vitreous, adamantine
Streak Light green
Specific gravity 3.7-3.8
Refractive index 1.624-1.626
Other characteristics 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.

References[edit]

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