A group of intergrown bournonite “cogwheel” twins showing classic form and nice lustre. These crystals are quite blocky and the prism faces on the right-hand crystal are particularly cool. These crystals grew against a matrix such that they are partial crystals, with interrupted growth on the one surface that contacted the matrix. In excellent condition, a couple minor nicks. A very nice bournonite!
About These Bolivian Bournonites
These bournonite crystals are from the Viboras Mine, Machacamarca District, Potosí, Bolivia. The locality has produced excellent bournonite specimens over the years, but the finds are have been sporadic, often years apart. The nature of the bournonite has varied from one find to the next, and some of the bournonite has been of modest lustre, sometimes dull, and of varying sharpness/definition. This latest find has produced sharp, lustrous bournonite crystals of the finest quality, exhibiting the classic “cogwheel” twinning.