Hydrated normal arsenate
Specific gravity: 3.57
Colour: White, colourless, translucent pale green (nickeloan), brownish pink (cobaltoan)
Talmessite is a rare secondary arsenate
typically formed in the oxidised zone of some
hydrothermal mineral deposits. It is an alteration product of
realgar, orpiment or
copper-nickel arsenides, associated with gaitite,
calcite and dolomite
At Luceram, Ales-Maritimes, France, talmessite is associated with baryte (Dana).
At the type locality, the Talmessi Mine, Esfahan Province , Iran, talmessite occurs in the oxidation zone asssociated with aragonite and dolomite (AM45.1315, Dana).
At Bou Azzer, Morocco, talmessite is quite widespread, although it is rare worldwide. Here it occurs inter-grown with roselite-beta on a dolomite matrix associated with wendwilsonite (Minrec 38.5).
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