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Formula: K2Mg(SO4)2.6H2O
Hydrated sulphate, picromerite group
Specific gravity: 2.028
Hardness: 2½
Streak: White
Colour: Colourless, white, reddish, yellowish, greyish, colourless in transmitted light
Solubility: Soluble in water
Environments
Fresh picromerite is colourless. Specimens may dehydrate to white, opaque
leonite.
Picromerite principally occurs in oceanic bedded salt deposits, as a volcanic sublimate in fumaroles and in a
sulphate-rich hydrothermal ore deposit. In oceanic salt deposits associated minerals include
halite, anhydrite,
kainite and epsomite
(HOM).
Localities
At the Chuquicamata mine, Chuquicamata District, Calama, El Loa Province, Antofagasta, Chile, picromerite is
associated with hohmannite,
metavoltine and
metasideronatrite
(HOM).
At the type locality, Mt Vesuvius, Somma-Vesuvius Complex, Naples, Campania, Italy, picromerite occurs in
active volcanic fumaroles
(Mindat).
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