Bournonite - Twin in "cog wheel" typical of the species - Les Malines, Saint-Laurent-le-Minier, Gard France Size of crystal 6 × 5 cm. — Photo: Didier Descouens · CC BY-SA 4.0
Bournonite
Also known as: Wheel ore.
A lead-copper-antimony sulfosalt prized for its 'cog-wheel' twinned crystals — miners called it wheel ore.
Intro adapted from Wikipedia (CC BY-SA).
Bournonite is an IMA-recognized mineral species in the sulfosalt class, with the chemical formula CuPbSbS₃.
It crystallizes in the orthorhombic crystal system (space group Pn2_1m). It is a member of the Bournonite structural group.
Key properties: Mohs hardness 2.5–3; specific gravity 5.83; typically gray or black; Steel-gray to iron-black streak; Brilliant to dull luster.
IMA symbol Bnn, grandfathered status — known before the IMA’s founding, named in 1805.
Found in hydrothermal veins formed at medium temperatures.
It is found associated with Galena, tetrahedrite, sphalerite, chalcopyrite, pyrite, stibnite, zinkenite, siderite, quartz, rhodochrosite, dolomite, barite.
In honor of Jacques Louis de Bournon (1751–1825), French crystallographer and mineralogist.
Collections: Collector Favorites, Metals & Native Elements.