Formula: Fe3+2O(SO4)2.7H2O
Hydrated sulphate
Crystal System: Triclinic
Specific gravity: 2.189 to 2.286
Hardness: 2½
Streak: Lemon yellow
Colour: Amaranth-red to brownish red and red-orange
Solubility: Decomposed by cold water with the formation of an insoluble basic salt, soluble in hydrochloric acid (Mindat)

Hydrothermal environments

Amarantite is a secondary mineral formed especially in arid climates. Associated minerals include hohmannite, fibroferrite, chalcanthite, copiapite, coquimbite and sideronatrite (HOM, Mindat).


The type locality is Caracoles, Sierra Gorda, Antofagasta Province, Antofagasta, Chile.

At the Chuquicamata Mine and at the Queténa Mine, Toki Cu deposit, both in the Chuquicamata District, Calama, El Loa Province, Antofagasta, Chile, amaranthite is found in the oxidised portions of massive quartz-pyrite veins, always associated with hohmannite and usually with fibroferrite. It occurs along the walls of small sulphate veins with the centres usually occupied by hohmannite and fibroferrite or in crystalline masses within the hohmannite. Amaranthite commonly forms in chalcanthite or melanterite variety pisanite, and is less commonly associated with fibroferrite than is hohmannite. Amaranthite forms later than all these minerals (AM 23.669-760).

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