Amarantite - Encyclopedia

    Class : Sulphates, chromates, molybdates
    Subclass : Hydrated sulphates
    Crystal System : Triclinic
    Chemistry : Fe₂(SO₄)₂O 7H₂O
    Rarity : Rare

Amarantite is a rare iron sulphate formed by the weathering of iron sulphides in an arid climate. Its name comes from the Latin amarantus (amaranth) in reference to its purple-red color. It is a secondary mineral which is part of a classic mineralogical procession to which other iron sulphides belong (copiapite, voltaite, jarosite, coquimbite, botryogen, fibreferrite, etc...), resulting like it from precipitation from acid natural sulfuric acid, formed by reaction of surface water with iron sulphides. By changing the conditions of the environment (temperature, pH, oxidation-reduction potential, etc...), these sulphates are easily hydrolyzed into ferric hydroxides (goethite, limonite, etc...). Amarantite forms elongated prismatic to acicular crystals, frequently flattened and strongly striated, united in radiating aggregates, of a brownish-red to dark red-orange ("amaranth") tint.

No twin report for this mineral species.