Mineral Species: Chalcocite, Cu2S (Copper Sulfide).

Mineral Notes: Chalcocite is an important ore of Copper and has been mined since the earliest of times. It is highly valuable because of its high metal content in proportion to weight (67% atomic ratio and nearly 80% by weight) and the ease with which copper can be extracted from the ore. Unfortunately it is relatively rare. The now exhausted Cornish mines produced the best clusters of wonderfully formed crystals. Since Chalcocite is a secondary mineral that forms from the alteration of other minerals, it very frequently forms pseudomorphs of other minerals.

Description: An irregulalry shaped matrix composed largely of clusters of silvery gray Chalcocite. Some crystalline habit is present, evident by the angular surface of the mineral. There are also numerous inclusions of waxy Quartz and in several places the Chalcocite is covered by crusts of crystalline Malachite. The combination of gray, white and green is very beautiful.

Location: South Caradon Mine, Cornwall, England.