GEMSTONES (21)

GEMSTONES (21)   Malachite Used as an ore of copper, a pigment, a gemstone, and a sculptural material for thousands of years. Malachite Gemstones:A malachite cabochon (30x40 millimeter) and a malachite puffed heart, both cut from rough mined in the Democratic Republic of the Congo. This oval cabochon shows the agate-like banding in various shades of green that is typical of malachite. The puffed heart shows concentric structures. What is Malachite? Malachite is a green copper carbonate hydroxidemineralwith a chemical composition of Cu2(CO3)(OH)2. It was one of the first ores used to producecoppermetal. It is of minor importance today as an ore of copper because it is usually found in small quantities and can be sold for higher prices for other types of use. Malachite has been used as agemstoneand sculptural material for thousands of years and is still popular today. Today it is most often cut into cabochons or beads for jewelry use. Malachite has a green color that does not fade over time or when exposed to light. Those properties, along with its ability to be easily ground to a powder, made malachite a preferred pigment and coloring agent for thousands of years. Botryoidal Malachite:Close-up of botryoidal malachite in a seafoam green color from Bisbee, Arizona. This view spans an area of the specimen about 5 millimeters wide and high. Specimen and photo by Arkenstone /www.iRocks.com. Where Does Malachite Form? Malachite is a mineral that forms at shallow depths within the Earth, in the oxidizing zone above copper deposits. It precipitates from descending solutions in fractures, caverns, cavities, and the intergranular spaces of porous rock. It often forms withinlimestonewhere a subsurface chemical environment favorable for the formation of carbonate minerals can occur. Associated minerals includeazurite,bornite,calcite,chalcopyrite,copper,cuprite, and a variety of iron oxides. Some of the first malachite deposits to be exploited were located in Egypt and Israel. Over 4000 years ago, they were mined and used to produce copper. Material from these deposits was also used to produce gemstones, sculptures, and pigments. Several large deposits in the Ural Mountains of Russia were aggressively mined, and they supplied abundant gem and sculptural material in the 1800s. Very little is produced from these deposits today. Much of the malachite entering the