Formula: Cu2+(AsO3OH).H2O
Hydrated normal arsenate
Specific gravity: 3.70
Hardness: 3 to 3½
Streak: Pale green
Colour: Light green to sea green
Solubility: Soluble in dilute hydrochloric acid

Hydrothermal environments

Geminite occurs as coatings on quartz (Webmin).


At the Salsigne mine, Salsigne, Carcassonne, Aude, Occitanie, France, geminite occurs on specimens from mine dumps at the gold-bearing arsenic sulphide deposit, associated with lindackerite, yvonite, arsenopyrite, bismuth, chalcopyrite and pushcharovskite (HOM).

At the type locality, Cap Garonne Mine, Le Pradet, Var, Provence-Alpes-Côte d'Azur, France, geminite occurs on quartz in an arsenic-bearing oxidised lead-copper deposit. Associated minerals include tennantite, covellite, chalcanthite, lavendulan, pushcharovskite, antlerite and brochantite (AM 77.671, HOM).

At the Khder Mine, Amerzgane, Ouarzazate Province, Drâa-Tafilalet Region, Morocco, geminite has been found as typical twins to 0.5 mm in a weathered piece of löllingite which mainly contained scorodite crusts and spherules of schneiderhöhnite (Minrec 38.5.375).

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