This transformation is reversible, with gypsum or calcium sulfate hemihydrate forming anhydrite by heating to around 200 °C (400 °F) under normal atmospheric conditions.

Anhydrite is most frequently found in evaporite deposits with gypsum; it was, for instance, first discovered in 1794 in a salt mine near Hall in Tirol.

In this occurrence, depth is critical since nearer the surface anhydrite has been altered to gypsum by absorption of circulating ground water.

Anhydrite occurs in a tidal flat environment in the Persian Gulf sabkhas as massive diagenetic replacement nodules.

[8] Interaction of anhydrite with hydrocarbons at high temperature in oil fields can reduce sulfate (SO2–4) into hydrogen sulfide (H2S) with a concomitant precipitation of calcite.

Extensive structural damage in the German city of Staufen im Breisgau has occurred since a 2007 geothermal drilling project allowed subsurface water to invade a layer of anhydrite below the city, causing extensive but uneven ground swelling as pockets of the anhydrite converted to gypsum.