925/000 silver ring with Malachite from Congo (Zaire)

The mineral azurite is a copper carbonate with the chemical formula Cu3 (CO3) 2 (OH) 2. The translucent to translucent typically azure azurite has a light blue stripe color, a glass luster and the crystal system is monoclinic. The average density is 3.83 and the hardness is 3.5 to 4. Azurite is non-radioactive and bright blue to dark purple pleochroic. The name azurite is derived from the Persian lazhward, which means "blue". The very common azurite occurs mainly in the oxidized parts of copper deposits or as a secondary mineral in carbonate-rich water. It is also formed when copper-containing solutions react with limestone. The type location of azurite is Chessy-les-Mines, Rhône-Alpes, France. Azurite has been used as a blue pigment for centuries. It used to be known as Azurro Della Magna (from Italian). When mixed with oil it turns slightly green. When mixed with egg yolk it turns gray-green. Azurite is often used in jewelry and is a popular mineral among collectors.

Malachite is a mineral that is used as a gemstone. It is a copper carbonate with the chemical formula Cu2CO3 (OH) 2. In nature it is often found together with the related azurite (Cu3 (CO3) 2 (OH) 2). The crystal structure is monoclinic and is mostly botryoidal in shape. The name of the mineral comes from the Greek and refers to the color of the mallow (mallow). Malachite was worked as a gemstone early on. In Egypt cameos, amulets and ornaments were made from it. The Greeks and Romans also knew malachite. The pulverized mineral was used as make-up and as a colorant for paint. Malachite was said to be able to protect children from sorcery and witchcraft. In ancient times it was thought that it could cure eye ailments. In the 16th century it was used in Central Europe to promote the growth of children and to relieve pain. Malachite is found worldwide. In Asia, significant amounts are found in China, India and the Urals in Russia, as well as in Australia. In the Americas, the most important supplies are in the Southwestern United States, mainly in the state of Arizona (a 4.5 ton block was found at Bisbee). Malachites in Mexico, Chile and Cuba are of gem quality. However, the most important and historically best known malachite reserves are in Africa. Here malachite has been mined since ancient times in the Copperbelt ("copper belt") in Congo-Kinshasa and Zambia. The malachite zone extends from the province of Katanga (Congo-Kinshasa) to Zambia. These malachites are considered the most beautiful and best in the world. Beautiful malachite crystals are found in Namibia (Tsumeb), Morocco, Zimbabwe and Angola. Europe has only small sites of little significance in Germany, Slovakia, Hungary, Romania, England, France. In Belgium, malachite is found in the Salm valley and in limestone in Visé. Malachite is formed in oxidation zones of copper deposits.