Malachite
Malachite is composed of 66% copper and can be used as an ore of copper. It usually forms in layered masses of radiating fibers, forming stalactitic formations which are often polished to beautiful bullseyes or bands. In Russia, it was a favorite stone of the Tsars and was made into columns, surfaces, and vases.
Chemistry: copper carbonate ♦ Opaque ♦ Luster: from silky to dull ♦ Crystal system: monoclinic prismatic ♦ Moh's hardness: 3.5-4 ♦ Color: bright green ♦ Localities: Ural mountains of Russia, DR Congo, and southwestern U.S. copper districts.