Eskolaite - Encyclopedia

    Class : Oxides and hydroxides
    Subclass : Oxides
    Crystal system : Trigonal
    Chemistry : Cr2O3
    Rarity : Very rare

Eskolaite is an extremely rare chromium oxide which is mainly found in chrome-bearing tremolite skarns, more rarely in metaquartzites and chlorite schists. It is also known in pebbles of fluvial alluvium and glacial moraines. Its name was given to it in honor of Pentii Eelis Eskola, Professor of Petrology at the University of Helsinki (Finland). Eskolaite appears in shiny rhombohedra of dark green to greenish black.

Main photo : Eskolaite from Outokumpu mining district, Outokumpu, North Karelia, Finland © Stephan Wolfsried

Eskolaite in the World

The best eskolaite crystals are 12 mm shiny rhombohedra that come from the Finnish Outokumpu deposit. Good crystals have been discovered at Nizhny Tagil in the Russian Urals. Unalterable, eskolaite is also found in tumbled crystals in the alluvium of Paramirim (Bahia, Brazil) as well as in Guyana.

Eskolaite in France

Eskolaite is not present in the French underground.

Twinning

No twin known for this mineral species.

Fakes and treatments

No fake listed for this mineral species.


Hardness : 8 to 8.5
Density : 5.18
Fracture : Undeterminated
Streak : Light green

TP : Translucent to opaque
RI : Undeterminated
Birefringence : Undeterminated
Optical character : Uniaxial
Pleochroism : Visible
Fluorescence : None

Solubility : Insoluble


Magnetism : None
Radioactivity : None