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Formula: Ca(AsO3OH).2H2O
Hydrated acid arsenate
Crystal System: Monoclinic
Specific gravity: 2.53 to 2.73 measured 2.73 calculated
Hardness: 2 to 2½
Streak: White
Colour: White or colourless, greyish white; colourless in transmitted light
Solubility: Readily soluble in acids; insoluble in water.
Environments:
Pharmacolite is an uncommon secondary mineral formed by oxidation of
earlier arsenic-bearing
minerals and commonly associated with haidingerite,
picropharmacolite and
hornesite
(HOM, Mindat). It dehydrates rapidly at 60°C to
haidingerite
(Mindat).
At the type locality, the Sophia Mine, Baden-Württemberg, Germany, pharmacolite is found on oxidised
arsenic ores, and may be post-mining. It is associated with calcium-rich
rösslerite and
haidingerite
(Mindat).
At Bou Azzer, Morocco, pharmacolite forms easily as a post-mining product and also in oxidation zones. In
vein 7 it occurs as aggregates on quartz associated with
picropharmacolite,
erythrite and, more rarely,
lavendulan. In vein 2 it occurs in arsenic-bearing
cobalt ores
associated with hematite,
spherocobaltite
and picropharmacolite. It has been found on
a diorite matrix with
gypsum and lavendulan.
At Méchoui and Ightem it is intergrown with picropharmacolite and
associated with heterogenite
(Minrec 38.5.387).
At the OK mine, Los Angeles county, USA, pharmacolite occurs with
erythrite
(Dana).
At White Caps mine, Nevada, USA, pharmacolite is found with other arsenates, especially
haidingerite
(Dana).
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