RAMMELSBERGITE

    Class : Sulfides and sulfosalts
    Subclass : Arsenides
    Crystal system : Orthorhombic
    Chemistry : NiAs2
    Rarity : Rare

Rammelsbergite is a nickel arsenide found in medium temperature hydrothermal veins containing cobalt, nickel and often silver. It is associated with other white arsenides such as skutterudite and safflorite, with nickeline and native bismuth. It is a polymorph of pararammelsbergite and krutovite. It was named in honor of the German chemist and mineralogist Karl Friedrich Rammelsberg. Rammelsbergite is generally massive with a fine-grained to fibroradiated structure, tin-white in color with a slight pinkish tint. Its crystals are rare, in short prisms measuring up to 1 mm and seem to constantly show polysynthetic twins. It is a locally important nickel ore.

Main photo : Pyrostilpnite from the Clara Mine, Germany © Carsten Slotta

Rammelsbergite in the World

Rammelsbergite has been encountered in almost all deposits with cobalt-nickel (and often silver) metallic mineralization. It is common in the "Ni-Co-Bi-Ag-U" veins of the German ore mountains, notably in Schneeberg (Saxony) and in those of the Harz (Eisleben, Mansfeld). Excellent samples were collected from the Cobalt nickel-cobalt mines (Ontario, Canada). Rammelsbergite is also known elsewhere, notably at the Mohawk mine (Michigan) and in several veins in Great Britain (Wanlockhead, Leadhills, Coniston...).

Right photo : Rammelsbergite pseudomorph after native silver from Medenec, Chomutov District, Czech Republic © Gerhard Brandstetter


Rammelsbergite in France

In France, rammelsbergite is known in the arseniferous veins of Ste-Marie-aux-Mines (Haut-Rhin). It was also reported in La Rabasse (Hérault), Kaymar (Aveyron), Villefranche-de-Rouergue (Aveyron) and in the Aure valley (Hautes-Pyrénées).

Twinning

Twins are known on {101}. Rammelsbergite pseudomorph after native silver are reported.

Fakes and treatments

No fakes listed for this mineral species.


Hardness : 5.5 to 6
Density : 7 to 7.2
Fracture : Irregular
Streak : Gray-black

TP : Opaque
RI : -
Birefringence : -
Optical character : -
Pleochroism : None
Fluorescence : None

Solubility : -

Magnetism : NoneRadioactivity : None