?The weight of diamonds is measured in carats. The word comes from carob, which is a bean that grows on the Ceratonia siliqua tree. The bean has an amazingly consistent weight of 0.2g. There are five carats to a gram and about 142 carats to the ounce.



?Fewer than 1,000 rough diamonds weighing more than 100 carats have ever been found.

?The first ever reference to diamonds is in the Bible in Exodus xxviii.18 and xxxix.11. It mentions a diamond mounted on a priest's breastplate.

?In 1796, Smithson Tennant (1761-1815), British scientist, was the first person to show that diamonds are made of carbon. The diamond is the only gem in the world made of a single element.

?Diamonds are 180 times harder than emeralds.

?Diamonds melt at 6,900 c, which is two and a half times the temperature needed to melt steel.

?Diamonds come from a rock called kimberlite. About 200 tonnes of kimberlite are mined for every carat of polished diamond.

The largest diamond ever found is called the Cullinan after Thomas Cullinan, who was president of the famous diamond company De Beers. The stone weighed 3,106 carats (621g) and was found in South Africa in about 1905. It was presented to King Edward VII, who had it cut to make 105 separate diamonds. One of the largest of these weighs 317.4 carats and is set in the British Imperial State Crown.