What is Bournonite?
Bournonite is a copper lead antimony sulphosalt valued for its high density, metallic lustre and distinctive cyclic twins. It is a classic mineral of polymetallic ore veins.
Mineralogy and structure
The formula is CuPbSbS3. Bournonite crystallises in the orthorhombic system, has hardness around 2.5-3 and high specific gravity due to lead and antimony.
Colour and appearance
Fresh material is lead grey to steel grey with metallic lustre. The most recognisable habit is the twinned cogwheel or wheel-like form, although tabular, prismatic and massive material also occurs.
Formation and localities
Bournonite forms in hydrothermal veins with galena, sphalerite, chalcopyrite, tetrahedrite and quartz. Important localities include Cornwall, Romania, Bolivia, Peru, Germany, China and Australia.
Collecting and care
The cyclic twins are highly desirable but can be fragile. Lead-bearing sulphosalts should be handled as display minerals, with clean hands and no cutting, grinding or jewellery use.
Bournonite and zodiac signs
Some symbolic mineral lists associate Bournonite with Scorpio or Capricorn because of its dark metallic appearance. These links vary between traditions and are not scientific.
Symbolic and esoteric associations
Esoteric writing may use bournonite as a symbol of interlocking forces and complex systems, inspired by its twinned crystals. This is metaphor, not evidence of an effect on people.
