Metatorbernite

(repeating unit)Cu(UO₂)₂(PO₄)₂·8(H₂O)IMA symbolMtor^[1]Strunz classification8.EB.10Crystal systemTetragonalCrystal classDipyramidal (4/m)
(same H-M symbol)Space groupP4/nIdentificationColourLight to dark greenCrystal habitFlat platesCleavagePerfectFractureBrittleMohs scale hardness2.5LustreVitreous, adamantineStreakLight greenSpecific gravity3.7–3.8Refractive index1.624–1.626Other characteristics RadioactiveReferences^[2][3][4]

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.

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