Kermesite - Encyclopedia

    Class : Sulfides and sulfosalts
    Subclass : Sulfides
    Crystal system : Triclinic
    Chemistry : Sb2S2O
    Rarity : Quite common

Kermesite is a secondary mineral typical of stibnite alteration in antimony deposits. Its name comes from the Persian qurmizq (dark red) in allusion to the color of the mineral. Kermesite generally occurs in fibroradiated aggregates of acicular crystals, up to 8 cm in radius, in capillary crystals or in powdery coatings. Its luster is adamantine to submetallic, its cherry red or blackish carmine red color is characteristic. In polished section (polarized light), it is a spectacular mineral : multi-colored with intense bright red internal reflections. It is an accessory ore of antimony.

Main photo : Kermesite from Lac Nicolet Mine, Quebec, Canada © Tony Peterson

Kermesite from Globe and Phoenix Mine, Zimbabwe © Eugene & Sharon Cisneros
Kermesite from Pezinok, Slovakia © Ladislav Turecky
Kermesite from Dafeng, Guangxi, China © Eugene & Sharon Cisneros
Kermesite from Lubilhac, Brioude, Haute-Loire, France © Pascal Chollet

Kermesite in the World

The Globe & Phoenix mine (Zimbabwe) provided superb fibroradiated masses made up of almost decimetric crystals. The most beautiful crystals certainly come from Dafeng (Guangxi, China), they appeared on the market in 2002-2003 and measure up to 15 cm. Beautiful samples also come from Braundorf (Germany), Pribram (Czech Republic), Cetine (Tuscany, Italy) as well as the Pezinok antimony mines near Bratislava (Slovakia).

Kermesite in France

In France, kermesite is known in the antimony mines of the Brioude-Massiac district (Haute-Loire and Cantal) and at the Chalanches mine (Isère) which also produced some quality samples.


Twins are known for this mineral species.

Fakes and treatments

No fakes recorded for this mineral species.

Hardness : 1 to 1.5
Density : 4.5 to 4.6
Fracture : Undetermined
Streak : Brown-red

TP : Translucent to opaque
RI : 2.720 to 2.740
Birefringence : 0.020
Optical character : Biaxial +
Pleochroism : None
Fluorescence : None

Solubility : -

Magnetism : NoneRadioactivity : None


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