ULLMANNITE

    Class : Sulfides and sulfosalts
    Subclass : Sulfides
    Crystal system : Cubic
    Chemistry : NiSbS
    Rarity : Uncommon

Ullmannite is a mineral of certain high-temperature hydrothermal veins of nickel and cobalt or copper, in which it is associated with other nickel minerals, mainly gersdorffite and nickeline, chalcopyrite or pyrrhotite. It forms a continuous series with willyamite, the cobalt pole of the series. It was named in honor of the German chemist and mineralogist Johann Christoph Ullmann who discovered the mineral. Crystallized ullmannite is most often cubic, with striated faces, more rarely octahedral, of steel gray to silvery white color. As and Bi contents are not rare. It is an ancillary ore of nickel.


Main photo : Ullmannite from Roc Blanc, Morocco © Joan Rosell

Ulmannite in the World

The best known crystals are 25 mm cubes on calcite, from the Italian mine of Masaloni (Sarrabus, Sardinia). Excellent 20 mm crystals have been extracted from German mines (Siegen and Wissen district), Austrian mines (Friesach and Hüttenberg), Moroccan (Roc Blanc) and Australian mines (Broken Hill).

Right photo : Ullmannite from Dörnberg Mine, Olsberg, Germany © Elmar Lackner


Ullmannite in France

Ullmannite is known in the mines around Brioude (Haute-Loire), Challanches (Isère), Poullaouen (Finistère), Oms (Pyrénées-Orientales) as well as in many other deposits.

Twinning

Twinning is known on [110].

Fakes and treatments

No fakes listed for this mineral species.


Hardness : 5 to 5.5
Density : 6.65
Fracture : Irregular
Streak : Black to gray

TP : Opaque
RI : -
Birefringence : 0
Optical character : None
Pleochroism : None
Fluorescence : None

Solubility : Nitric acid

Magnetism : NoneRadioactivity : None