Hydrated normal arsenate
Specific gravity: 3.57
Colour: White, colorless, translucent pale green (nickelian), brownish pink (cobaltian)
Talmessite is a rare secondary species
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,
erythrite, annabergite, picropharmacolite, pharmacolite,
calcite and dolomite.
At Luceram, Ales-Maritimes, France, talmessite is associated with baryte.
At the type locality, the Talmessi Mine, Esfahan Province , Iran, talmessite occurs in the oxidation zone asssociated with aragonite and dolomite.
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.
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