Goslarite - Encyclopedia

    Class : Sulfates, chromates, molybdates
    Subclass : Hydrated sulfates
    Crystal system : Orthorhombic
    Chemistry : ZnSO4 7H2O
    Rarity : Quite common

Goslarite is a secondary zinc sulfate that forms by oxidation of sphalerite. It is frequently a recently formed mineral, common in efflorescences and stalactites in mine shafts and galleries. It is also found in certain slags. By artificial replacement of Zn by Mg, a solid solution is obtained with epsomite. It owes its name to its discovery location : the Rammelsberg mine near Goslar (Germany). Goslarite is colorless to yellowish white, sometimes brownish or greenish. The synthetic crystals are chunky prismatic, while the efflorescences and stalactites take on a fibrous texture.

Main photo : Goslarite colored by copper from Esperanza Mine, Lavrion, Greece © Fritz Schreiber

Goslarite in the World

Goslarite is common in efflorescence in many American mines (Bingham, Galena, Comstock Lode, etc...). Goslarite encrustations are known in the Spanish sulfidic masses of Almagrera (Andalusia), and the German Rammelsberg (Harz).

Goslarite in France

In France, goslarite is known in green incrustations (copper variety) at La Rabasse, near Ceilhes (Hérault). It is also reported in Chessy (Rhône), in Cap Garonne (Var), in La Minette near Alès (Gard) and in Orpierre (Hautes-Alpes).


No twin known for this mineral species.

Fakes and treatments

No fakes recorded for this mineral species.

Hardness : 2 to 2.5
Density : 1.97
Fracture : Fibrous
Streak : White

TP : Translucent to transparent
RI : 1.447 to 1.485
Birefringence : 0.023
Optical character : Biaxial -
Pleochroism : None
Fluorescence : None

Solubility : Water

Magnetism : NoneRadioactivity : None


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