Mineral Species: Bournonite

Chemical Formula: CuPbSbS3

Chemical Name: Copper Lead Antimony Sulphide

Mineral Class: Sulphide

Mineral Notes: Bournonite is a very popular collector mineral because of the striking silvery-grey crystals which have a strong tendency to form radiating (cogwheel-like) aggregates. For this reason Cornish miners, where particulalry striking specimens were once found, knew the mineral as cogwheel ore. Similarly, in Germany the mineral is known as Radelrz, or wheel ore

Description: A white, highly crystalline Quartz matrix on which sit several cog-wheel aggregates of Bournonite. Many go right through the matrix and can be seen on both sides. All have a grey-black colour and a sub-metallic luster. A ver attractive display specimen.

Location: Treveglos Mine, St Merryn, Cornwall, England.