Chemical composition -- A hydrated copper silicate.
Color -- Bluish green to intense green.
Optics -- R.I. 1.64-1.71.
Durability -- Hardness 5. Brittle, with one direction of perfect cleavage. Too fragile for jewelry use.
Crystal structure -- Hexagonal .
Specific Gravity -- 3.28-3.35.
Sources -- Occurs in copper mines throughout the world, but the best crystals come from Tsumeb, Namibia. Faceted stones are rare and always under 2 carats.