Haidingerite is a calcium arsenate mineral with formula Ca(AsO3OH)·H2O.

It typically occurs as scaly, botryoidal or fibrous coatings.

It was named to honor Austrian mineralogist Wilhelm Karl Ritter von Haidinger (1795–1871).

[3] It occurs as a dehydration product of pharmacolite in the Getchell Mine, Nevada.

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