Azurite is a secondary mineral, a hydrated copper carbonate, crystal symmetry monoclinic, chemical formula (Cu3(CO3)2(OH)2. It occurs both in crystalline form but more frequently as an amorphous precipitate. Its name refers to its color, a deep azure-blue that makes it popular as a collector's item, but only rarely used in body-jewelry on account of its susceptibility to wear and color loss. In medieval times, the mineral was ground into fine powder and used by painters as a blue pigment. The azurite in this sample is a sub-crystalline precipitate on a rock substrate that shows a thin coating of a green mineral, most probably malachite. Actual width is 140 mm.