Of all precious stones, diamond has been and is the most desired, though it does not have the attractive colour of emerald or ruby. Over the centuries this passion for diamonds has endowed the stones with histories that are rich with mysticism, intrigue, adventure and romance. Found rarely in nature, the gemstone is the hardest and most durable material on earth. More important, the mining and sale of diamond has been so rigidly controlled, that the price of the stones has been increasing steadily over the last three centuries.
Chemists and crystallographers have determoned that the diamond is merely pure carbon crystallised in a structure different from that of common graphite and charcoal. As early as 1675 AD, sir Isaac Newton concluded that diamond would burn in air and twenty years later, Averani and Targioni demonstrated this at the Accademia del Cimento of Florence. They put a diamond in the intense heat of a fierce charcoal fire and saw the stone gradually decrease in size and finally disappear.
Millions of years ago, organic material such as trees or other living creatures died and exposed to the heat of those times, became charcoal. This carbon, trapped within molten rock and subjected to intense pressures and temperatures of over 3000C over the thousands of years, slowly crystallised into clear hard diamonds. Natural volcanic eruptions took the material to the surface of the earth. Later, erosion by the sun and rain and other climatic changes broke up the soil containing the diamonds and scattered it and the gemstones over river beds. These 'alluvial' deposits are found on the surface of river beds, on the rough pebbled sea bed or in gravel down to twenty meters beneath the sand. Diamonds are also mined by digging within the bluish ground of 'Kimberlite' from deep inside the earth, down volcanic pipes of around half a kilometers diameter through which molten material once forced its way up. A productive mine usually yields a gram of diamonds from about three-hundred tonnes of ore.