Copper(II) carbonate (often called copper carbonate or cupric carbonate) is a blue-green compound (chemical formula CuCO3) forming most of the patina one sees on weathered brass, bronze, and copper. The color can vary from bright blue to green, because there may be a mixture of both copper carbonate and basic copper carbonate in various stages of hydration. It was formerly much used as a pigment, and is still in use for artist's colours.
It is also been used in some types of make-up, like lipstick etc...It can also be extremely poisonous to humans.
Basic copper(II) carbonate occurs naturally as malachite (CuCO3.Cu(OH)2) and azurite (Cu3(CO3)2(OH)2).