Antlerite is a hydrous copper sulphate of medium to dark green colour that often occurs as fibrous or acicular crystals with a vitreous lustre. The crystal system is orthorhombic. It is the main ore in the oxidized zones of several copper mines around the world, such as the Antler mine in Arizona from which it derives its name. This sample is from a mine in Chile. Actual width is 60 mm.