Class : Sulfates, chromates, molybdates
    Subclass : Hydrated sulfates
    Crystal system : Trigonal
    Chemistry : Fe(SO₄)(OH) 5H₂O
    Rarity : Rare to uncommon

Fibroferrite is a rare iron sulfate formed by alteration of iron sulfides, mainly in arid climates. It is a secondary mineral which is part of a procession to which other iron sulfates belong (copiapite, voltaite, jarosite, coquimbite, botryogen, etc...), resulting like it from precipitation from natural sulfuric acid formed by reaction of surface water with iron sulphides. By changing environmental conditions (temperature, pH, redox potential, etc...) these sulfates are easily hydrolyzed into ferric hydroxides (goethite or limonite). Fibroferrite is easily subject to dehydration at room temperature. Its name derives from the Latin fibra (fiber) and ferrum (iron) in allusion to its fibrous habit and its chemical composition. It essentially forms fibrous masses, sometimes botryoidal, and encrustations composed of white, yellowish to yellowish-green, sometimes green or light brown, acicular to bacillary crystals.

Main photo : Fibroferrite from Trenning graphite mine, Mühldorf, Austria © Christian Auer

No twins known for this mineral species.

No fakes recorded for this mineral species.