Mineral Species: Chalcocite and Fluorite

Chemical Formula: Cu2S

Chemical Name: Copper Sulfide

Mineral Class: 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. Since Chalcocite is a secondary mineral that forms from the alteration of primary copper sulphide ores, it frequently forms pseudomorphs. 

Description: Black, crystalline grains of Chalcocite embedded in a grey banded matrix. The mineral has a very strong metallic luster and very definite crystal form. Interspersed in the matrix are elongated crystals of purple Fluorite. These are well-formed and lustrous. The combination of minerals is unusual and aesthetic.

Location: Hall Mine, Tonopah, Nevada, USA.