Class : Sulfates, chromates, molybdates
    Subclass : Anhydrous sulfates
    Crystal system : Trigonal
    Chemistry : NaFe₃(SO₄)₂(OH)₆
    Rarity : Rare to uncommon

Natrojarosite is a double sulfate of sodium and iron. It is a secondary mineral formed by alteration of iron sulfides, mainly in arid climates. It is frequently associated with jarosite, with which however there does not seem to be a continuous solid solution. Natrojarosite, like jarosite, results from precipitation from "natural" sulfuric acid, formed by reaction of surface water with iron sulfides. By changing environmental conditions (temperature, pH, redox potential, etc...), natrojarosite and jarosite are easily hydrolyzed into ferric hydroxides (goethite and limonite). Its name derives from its chemical composition : from the Latin natrium (sodium), and its chemical analogy with jarosite. Natrojarosite usually occurs in encrustations, in compact granular, concretionary or earthy masses, rarely in very small, flattened rhombohedral crystals. It is ocher-yellow to brownish orange in color, sometimes pale orange.

Main photo : Natrojarosite from Gilbert Mining District, Nevada, USA © Douglas Merson

No twins known for this mineral species.

No fakes recorded for this mineral species.