‘Diamond is forever’ is a very common phase. Have you wondered why? Diamond is the most precious and enduring material in the world. It is the hardest material known. It cannot be cut by any metal, or for that matter by any other thing except by another diamond. Metal saw impregnated with diamond powder is used for cutting diamonds in industries. Diamond is nothing but a pure crystalline form of carbon, which is obtained from mines. At 900°C, it starts burning slowly and combines with atmospheric oxygen to form carbon dioxide. At 1000°C, it gets converted into graphite. At higher temperatures, the rate of formation of graphite is faster. Diamond is a good conductor of heat but a bad conductor of electricity. Its thermal conductivity is five times greater than that of copper. Diamonds vary in colours; they are either colourless or found in green, brown, and white, yellow, pink and sometimes black colours. Until 1955, diamond was obtained only from mines but later, certain synthetic methods for its manufacture were also developed. Diamond obtained from mines is called natural diamond, whereas the one made by synthetic methods is called artificial diamond. Africa is the biggest source of natural diamonds. About 80% of diamonds in the world come from this continent. Before they come to the market for sale, they are cut into different shapes and polished. Diamonds retain their original sparkle even after hundred of years. The General Electric Company of U.S.A. made synthetic diamonds for the first time in the world in 1955. In the synthetic process, diamonds are produced from graphite. In high temperature furnaces, graphite is heated to about 3000°C under high pressure. By doing so graphite is converted into diamond. Synthetic diamond resembles the natural diamond in many respects. These are generally used in jewellery and industry. Industrial or inferior diamonds are also used for drilling and grinding. The weight of the diamond is measured in carats. One carat is equal to about 200 milligrams. The biggest producers of diamonds are Africa, India, Indonesia, Brazil, Australia and the U.S.S.R.