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 in the World
Twinning
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