Berthierite - Encyclopedia

    Class : Sulfides and sulfosalts
    Subclass : Sulfosalts
    Crystal System : Orthorhombic
    Chemistry : FeSb2S4
    Rarity : Fairly common

Berthierite is an iron and antimony sulphide found in low and medium temperature hydrothermal veins, in common association with quartz, baryte and stibnite. It was named in honor of the French chemist Pierre Berthier who was the first to study this mineral. The free crystals are elongated, frequently acicular, striated longitudinally according to [001]: they remain however exceptional and very rarely exceed the centimeter. Berthierite usually occurs in fibrous masses (more common than for stibnite), feathery or radiate up to 6 cm in radius, or in grainy masses. When fresh, berthierite has a steel-gray color similar to stibnite, but it quickly becomes iridescent and dulls in air, sporting a bronze patina that browns over time. Berthierite easily oxidizes at outcrops to a mixture of antimony and iron oxides ("chocolate" oxides) which usually retain the fibrous appearance of the replaced mineral. Berthierite is an antimony ore less appreciated than stibnite because of its lower content of this metal (57% against 72%) and its more difficult roasting.

Main photo : Berthierite from Herja, Mamures, Romania © Lopatkin Oleg

Berthierite from the Charbes vein, Lalaye, Bas-Rhin, France © Pascal Chollet
Berthierite and quartz from Slany, Czech Republic © Bohuslaves Bures
Berthierite from Gründelwald, Germany © Joachim Esche
Berthierite from Massagette, Pontgibaud, Puy-de-Dôme, France © Joachim Esche

Berthierite in the World

Beautiful 1 cm free crystals, probably the best known, come from polymetallic mines in the Baia Mare region of Romania (Herja and Baia Sprie). Berthierite is abundant in the antimony mines of the Gravelote district (South Africa). It is also present in Pribram and Kutna Hora (Czech Republic), Nakaze (Japan), etc...

Berthierite in France

In France, berthierite was abundant in many mines in Auvergne (Chazelle, Marmeissat, Osfonds, Le Fraisse, Pontgibaud...) which yielded interesting specimens. It was the dominant antimony ore at the Lisette mine near Osfonds (Haute-Loire). It is found in many other localities: Lalaye (Bas-Rhin), Biards mine (Haute-Vienne), etc...

Twinning and special crystallizations

No known twin for this mineral species.

Fakes and treatments

This mineral can be confused with the stibine with which it shares deposits. Some unscrupulous Asian sellers also call carborundum (synthetic silicon carbide) berthierite to make it easier to sell.

Hardness : 2 to 3
Density : 4,64
Fracture : Irregular
Trace : Gray brown

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

Solubility : Hydrochloric acid

Magnetism : None
Radioactivity : None


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