Mineral Species: Bournonite

Chemical Formula: CuPbSbS3

Chemical Name: Copper Lead Antimony Sulphide

Mineral Class: Sulphide

Mineral Notes: Bournonite is a popular collector mineral because of the striking silvery-grey crystals which have a strong tendency to form radiaiting (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 solid matrix of Bournonite on whose upper surface lie several overlapping crystals. These are very well formed and the cogwheel form can be seen. Amonst the crystals are small crystals of white Quartz which provide a very attractive contrast to the dark-grey metallic Bournonite

Location: Huaron Mine, Cerro de Pasco, Peru.