Ferrinatrite - Encyclopedia
Class : Sulfates, chromates, molybdates
Subclass : Hydrated sulfates
Crystal system : Trigonal
Chemistry : Na3Fe(SO4)3 3H2O
Rarity : Uncommon
Ferrinatrite is a double sulfate of sodium and iron. It is a rare secondary mineral, formed by alteration of iron sulphides, mainly in arid climates. It is also found in fumarolic deposits. It is part of a classic mineralogical procession to which other iron sulphates belong (melanterite, jarosite, coquimbite, botryogen, etc...) which, like it, result 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-limonite). Its name comes from its chemical composition : iron + sodium (natrium in Latin). Ferrinatrite occurs in the form of short prismatic crystals, cleavable masses or fibrous aggregates, colorless, white or yellow.
Main photo : Ferrinatrite from Le Cetine di Cotorniano Mine, Chiusdino, Siena Province, Tuscany, Italy © Giuseppe Finello
Ferrinatrite in the World
Twinning
No twin known for this mineral species.
Fakes and treatments
No fakes recorded for this mineral species.
Hardness : 2.5
Density : 2.55 to 2.61
Fracture : Irregular
Streak : White
TP : Transparent
RI : 1.556 to 1.613
Birefringence : 0.054
Optical character : Uniaxial +
Pleochroism : None
Fluorescence : None
Solubility : Water
Magnetism : None
Radioactivity : None