Torbernite

Not to be confused with Tobermorite or Torbanite.
Torbernite
Torbernite crystals from Mashamba West Mine, Kolwezi, Katanga Province, Democratic Republic of the Congo
General
CategoryPhosphate minerals
Formula
(repeating unit)		Cu[(UO2)(PO4)]2(H2O)12[1]
IMA symbolTor[2]
Strunz classification8.EB.05
Crystal systemTetragonal
Crystal classDitetragonal dipyramidal (4/mmm)
H-M symbol: (4/m 2/m 2/m)[3]
Space groupI4/mmm[4]
Identification
Formula mass641 – 713 g/mol, depending the degree of water loss
ColorEmerald green to apple green[5]
Crystal habitTabular crystals; Foliated to earthy masses and encrustations
TwinningRare on [110]
Cleavage[001] Perfect; [100] Distinct[5]
FractureBrittle[5]
Mohs scale hardness2–2.5[5]
LusterVitreous; pearly[5]
StreakPale green
DiaphaneityTransparent to subtranslucent
Densitymeasured: 3.22; calculated: 3.264(1)[5]
Optical propertiesUniaxial (−)
Refractive indexnω = 1.590 – 1.592 nε = 1.581 – 1.582[3]
Birefringenceδ = 0.009 – 0.010[3]
PleochroismVisible
Melting pointDecomposes before
FusibilityDecomposes before
Other characteristics Radioactive and Poisonous

Torbernite, also known as chalcolite,[6] is a relatively common mineral with the chemical formula Cu[(UO2)(PO4)]2(H2O)12.[1] It is a radioactive, hydrated green copper uranyl phosphate, found in granites and other uranium-bearing deposits as a secondary mineral. The chemical formula of torbernite is similar to that of autunite in which a Cu2+ cation replaces a Ca2+ cation. Torbernite tends to dehydrate to metatorbernite with the sum formula Cu[(UO2)(PO4)]2(H2O)8.

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