Specific gravity: 2.98
Hardness: 3 to 3½
Colour: Colourless, white, grey, blue
Solubility: Moderately soluble in hydrochloric, sulphuric and nitric acid
Sedimentary environments (typical)
Anhydrite occurs in chemical sedimentary deposits and in the oxidation zone of high temperature hydrothermal
replacement deposits. It is found in
limestone and in some
amygdaloidal cavities in basalt.
It is a common alteration mineral in some porphyry (rock with coarse phenocrysts in a finer groundmass)
copper deposits, particularly those associated with diorite and
granodiorite intrusions. Gypsum
is a common associate
In carbonatites it is associated with baryte and gypsum (AS).
anhydrite and water to gypsum
Ca(SO4) + 2H2O ⇌ Ca(SO4).2H2O
Gypsum is frequently formed by the hydration of anhydrite.
Common impurities: Sr,Ba,H2O
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