Diamond
Diamond is the hardest known natural material (third-hardest known material below aggregated diamond nanorods and ultrahard fullerite), and is the more costly of the two best known forms (or allotropes) of carbon, whose hardness and high dispersion of light make it useful for industrial applications and jewellery. (The other equally well known allotrope is graphite.) Diamonds are specifically renowned as a material with superlative physical qualities ? they make excellent abrasives because they can be scratched only by other diamonds, Borazon, ultrahard fullerite, or aggregated diamond nanorods, which also means they hold a polish extremely well and retain luster. About 130 million carats (26,000 kg) are mined annually, with a total value of nearly USD $9 billion.[citation needed] About 100 tons are synthesized annually.[1]
The name ?diamond? derives from the ancient Greek adamas (αδάμας; ?invincible?). They have been treasured as gemstones since their use as religious icons in India at least 2,500 years ago? and usage in drill bits and engraving tools also dates to early human history.[citation needed] Popularity of diamonds has risen since the 19th century because of increased supply, improved cutting and polishing techniques, growth in the world economy, and innovative and successful advertising campaigns. They are commonly judged by the ?four Cs?: carat, clarity, color, and cut. Although synthetic diamonds are produced each year at nearly four times the rate of natural diamonds, the vast majority of synthetic diamonds produced are small imperfect diamonds suitable only for industrial-grade use.[citation needed]
Roughly 49% of diamonds originate from central and southern Africa, although significant sources of the mineral have been discovered in Canada, India, Russia, Brazil, and Australia. They are mined from kimberlite and lamproite volcanic pipes, which brought to the surface the diamond crystals from deep in the Earth where the high pressure and temperature enables the formation of the crystals. The mining and distribution of natural diamonds are subjects of frequent controversy such as with concerns over the sale of conflict diamonds by African paramilitary groups. There are also allegations that the De Beers Group misuses its dominance in the industry to control supply and manipulate price via monopolistic practices, although in recent years the company's market share has dropped to below 60%.[citation needed]
