Home > Metallic Minerals – September 17 > MS1440 Chalcocite after Bornite

Chalcocite after Bornite - Sold

Chalcocite and bornite are both copper sulfides, although bornite additionally contains iron. In the process known of supergene enrichment, sulfide minerals oxidize, releasing sulfur and iron atoms, leaving behind copper atoms. This process locally increases copper concentrations in ore deposits. Bornite has a Cu:S ratio of 5:4, while chalcocite has a ratio closer to 2:1.

This pseudomorph of a trapezohedral bornite crystal, 2.9 cm across, is faithfully preserved in sooty black chalcocite. A small miniature. This is the same locality for the best of species wittichenite.