The hardness of diamond and its high dispersion of light—giving the diamond its characteristic "fire"—make it useful for industrial applications and desirable as jewelry.Diamonds are such a highly traded commodity that multiple organizations have been created for grading and certifying them based on the "four Cs", which are color, cut, clarity, and carat.The various smaller mining companies were amalgamated by British imperialist Cecil Rhodes and Charles Rudd into De Beers, and The Kimberley under Barney Barnato.
In the twentieth century, gemologists have developed methods of grading diamonds and other gemstones based on the characteristics most important to their value as a gem.
Though popularly believed to derive its value from its rarity, gem-quality diamonds are quite common compared to rare gemstones such as alexandrite, and annual global rough diamond production is estimated to be about 130 million carats (26 tonnes; 29 short tons).
Another Indian description written in the beginning of the 3rd century describes strength, regularity, brilliance, ability to scratch metals, and good refractive properties as the desirable qualities of a diamond.
It is too early to assess the effect of future wide availability of gem-quality synthetic diamonds on the diamond market, although the traditional diamond industry has taken steps to try to create a distinction between diamonds dug from the ground and diamonds made in a factory, in part by downplaying the fact that diamonds from both sources are actually visually identical.
The most familiar usage of diamonds today is as gemstones used for adornment—a usage which dates back into antiquity.