Franckeite

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All minerals 1€ to 20€ 20€ to 100€ 100€ to 250€ Up to 250€All minerals 1€ to 20€ 20€ to 100€ 100€ to 250€ Up to 250€

Class : Sulfides and sulfosalts
Subclass : Sulfides
Crystal system : Triclinic
Chemistry : FePb₅Sn₃Sb₂S₁₄
Rarity : Rare

Franckeite is a very rare lead and tin sulfide present in certain tin-bearing hydrothermal veins, mainly in Bolivia. It was named in honor of the two German mining engineers Carl and Ernest Francke, pioneers of Bolivian geology in the 19^th century. Franckeite occurs in fine, lamellar crystals, more rarely elongated and grooved on {010}, often curved, but more commonly in masses, with a foliated or radiated appearance, in multicentimetric spherical aggregates, in rosettes or cauliflowers reaching 1 cm in diameter. Franckeite is lead gray to gray-black in color. It is a very minor ore of tin.

Main photo : Franckeite de San José Mine, Oruro, Cercado Province, Oruro, Bolivia © Oleg Lopatkin

Franckeite of San José Mine, Oruro, Cercado Province, Oruro, Bolivia © Brian Kosnar

Franckeéite of San José Mine, Oruro, Cercado Province, Oruro, Bolivia © Gianfranco Ciccolini

Franckeite from San José Mine, Oruro, Cercado Province, Oruro, Bolivia © E. & S. Cisneros

Franckeite from Siglo Veinte Mine, Llallagua, Potosí, Bolivia © Tony Peterson

Franckeite in the World

Franckeite is best known in the tin-bearing veins of Bolivia, where most of the well-individualized crystals come from, some exceeding 6 cm and grouped in tufted aggregates (Poopo, juanuni, Chocaya, Llallagua...). Franckéite is also known elsewhere, notably at Renison Bell (Tasmania, Australia) and in California, at Kalkar, near Santa Cruz, and at Thompson, near Darwin.

Franckeite in France

In France, franckéite forms microscopic areas in the wolframite vein of Vens-Haut (Puy-de-Dôme).

Twinning

No twin known for this mineral species.

Fakes and treatments

No fakes recorded for this mineral species.

Hardness : 2.5 to 3
Density : 5.90
Fracture : Irregular
Streak : Grey-Black

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

Solubility : Nitric acid

Magnetism : None
Radioactivity : None

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FRANCKEITE

Franckeite in the World

Twinning

Fakes and treatments

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
By classes By crystal systems By chemistry Mineral list
Minerals for sale Encyclopedia Glossary