Jamesonite - Encyclopedia

Class : Sulphides and sulfosalts
Subclass : Sulfosalts
Crystal system : Monoclinic
Chemistry : Pb₄FeSb₆S₁₄
Rarity : Uncommon

Jamesonite is an uncommon sulfosalt of mid-temperature lead-antimony hydrothermal veins. Its name was given to it in honor of the Scottish mineralogist Robert Jameson. It is found, like boulangerite, semseyite, zinkenite or plagionite, in veins with a dominant stibnite invaded by lead fluids, or in veins with galena and sphalerite infiltrated by antimony fluids. It appears in fibrous, acicular or filiform crystals, sometimes prismatic striated according to elongation, or in fibrous masses. Jamesonite readily weathers at outcrops to mixtures of antimony and lead oxides. The color is lead gray and the luster metallic. It is occasionally an ore of antimony, more rarely of lead.

Jamesonite in the World

Splendid aggregates made up of fluffy or fibrous tufts come from Baia Sprie (Romania), from Pribram (Czech Republic). But the most remarkable samples come from mines in the district of Fresnillo (Zacatecas, Mexico): they are fibrous masses composed of acicular crystals reaching 5 cm by 3 mm. Masses of fibrous crystals are also known in English Cornwall (district of St-Endellion), and in Bolivia (Huanuni, Machacamarca).

Jamesonite in France

In France, jamesonite was common in the Peschadoires vein (Pontgibaud, Puy-de-Dôme), in several antimony veins in the Massiac region (Cantal), and in the gold-bearing veins of Pontvieux (Puy-de-Dôme).

Twinning

Twins are known on {100}.

Fakes and treatments

No fake identified for this mineral species.

Hardness : 2.5
Density : 5.63
Fracture : Irregular
Streak : Gray-black

TP : Opaque
RI : Not measurable
Birefringence : Not measurable
Optical character : None
Pleochroism : None
Fluorescence : None

Solubility : Nitric acid

Magnetism : None
Radioactivity : None