Hydrated acid arsenate
Specific gravity: 2.58
Hardness: 1 to 2
Colour: White, colorless in transmitted light
Picropharmacolite is a secondary mineral formed in
the oxidation zone of arsenic ore deposits.
It is an oxidation product of arsenic-bearing sulphides in reaction with surrounding
calcium-rich rocks, or as a recent efflorescence in mine workings. Associated minerals include
The natural arsenates, including picropharmacolite, form at very low pressure and temperature in the oxidation zone of mineral deposits that contain arsenic.
At the Shimen mine, Hunan, China, picropharmacolite lines vugs in massive realgar.
At the type locality, the ore dumps of the Richelsdorf Smelter, Hesse, Germany, picropharmacolite is found as surface weathering of arsenic-bearing ores.
At Bou Azzer, Morocco, picropharmacolite is very common, sometimes associated with sainfeldite. At the Aghbar mine it is associated with erythrite, sainfeldite and pharmacolite, and at the Méchoui deposit it is associated with erythrite and spherocobaltite.
At Joplin, Missouri, USA, picropharmacolite has been found as a coating on dolomite.
At the White Caps mine, Nye county, Nevada, USA, picropharmacolite is associated with realgar, gypsum and sulphur.
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