Description
The mineral azurite is a copper carbonate with the chemical formula Cu3(CO3)2(OH)2. The typically transparent to translucent azurite has a light blue streak color, a vitreous luster, and a monoclinic crystal system. Its average density is 3.83 and its hardness is 3.5 to 4. Azurite is not radioactive and bright blue to dark purple pleochroic. The name azurite is derived from the Persian word lazhward, meaning "blue." The very common azurite occurs primarily in the oxidized portions of copper deposits or as a secondary mineral in carbonate-rich waters. It also forms when copper-bearing solutions react with limestone. The type locality of azurite is Chessy-les-Mines, Rhône-Alpes, France. Azurite has been used for centuries as a blue pigment. It was formerly known as Azurro Della Magna (from the Italian). When mixed with oil, it turns slightly green. When mixed with egg yolk, it turns grayish-green. Azurite is often used in jewelry and is a popular mineral among collectors.
Malachite is a mineral used as a gemstone. It is a copper carbonate with the chemical formula Cu2CO3(OH)2. It is often found in nature together with the related azurite (Cu3(CO3)2(OH)2). The crystal structure is monoclinic and usually botryoidal. The mineral's name comes from Greek and refers to the color of the mallow plant. Malachite was used as a gemstone from early times. In Egypt, cameos, amulets, and ornaments were made from it. The Greeks and Romans also knew malachite. The pulverized mineral was used as makeup and as a dye. It was said that malachite could protect children from sorcery and witchcraft. In antiquity, it was believed to cure eye ailments. In the 16th century, it was used in Central Europe to promote growth in children and to relieve pain. Malachite is found worldwide. In Asia, significant quantities are found in China, India, and the Urals in Russia, as well as in Australia. On the American continent, the main deposits are located in the southwestern United States, primarily in Arizona (a 4.5-ton block was found near Bisbee). Malachites in Mexico, Chile, and Cuba are of gemstone quality. However, the most important and historically well-known malachite reserves are in Africa. Here, malachite has been mined since ancient times in the Copperbelt in the Democratic Republic of the Congo and Zambia. The malachite zone extends from Katanga Province (Democratic Republic of the Congo) to Zambia. These malachites are considered the finest and best in the world. Beautiful malachite crystals are found in Namibia (Tsumeb), Morocco, Zimbabwe, and Angola. Europe has only small, insignificant deposits in Germany, Slovakia, Hungary, Romania, England, and France. In Belgium, malachite is found in the Salm Valley and in limestone at Visé. Malachite is formed in oxidation zones of copper deposits.
