world's largest diamond was the Cullinan, found in South Africa in 1905. It weighed 3,106.75 carats uncut. It was cut into the Great Star of Africa, weighing 530.2 carats, the Lesser Star of Africa, which weighs 317.40 carats, and 104 other diamonds of nearly flawless colour and clarity. They now form part of the British crown jewels.

The Cullinan was three times the size of the next largest diamond, the Excelsior, which was also found in South Africa. The world's largest documented polished diamond - unearthed in 1986, also in South Africa - is called Unnamed Brown. It weighs 545 carats and was cut down from a 700 carat rough diamond. It took an international team of expert cutters 3 years to complete the masterpiece. Another impressive diamond that also took 3 years to cut, and also is part of the British crown jewels, is the Centenary Diamond. It weighs 273.85 carats and is the world's largest flawless diamond.

Not all diamonds are white. Impurities lend diamonds a shade of blue, red, orange, yellow, green and even black. Vivid blue, green and pink diamonds are the rarest. They are not the rarest gemstones, however. That title goes to a pure red ruby. Diamonds actually are found in abundance; thousands are mined every year. 80% of them are not suitable for jewellery - they are used in industry.