The Koh-i-Noor (Persian for Mountain of Light; also spelled Koh-i-Nûr and Kooh-è Noor) is a large, colourless diamond that was found near the city of Guntur, India, possibly in the 13th century. It weighed 793 carats (158.6 g) uncut and was first owned by the Kakatiya dynasty. The stone changed hands several times between various feuding factions in South Asia over the next few hundred years, before ending up in the possession of Queen Victoria after the British conquest of the Punjab in 1849.
In 1852, Prince Albert, the husband of Queen Victoria, unhappy with its dull and irregular appearance, ordered it cut down from 186 carats (37.2 g). It emerged 42 per cent lighter as a dazzling oval-cut brilliant weighing 105.6 carats (21.12 g) and measuring 3.6 cm x 3.2 cm x 1.3 cm. By modern standards, the cut is far from perfect, in that the culet is unusually broad, giving the impression of a black hole when the stone is viewed head-on; it is nevertheless regarded by gemmologists as being full of life. As the diamond’s history involves a great deal of fighting between men, the Koh-i-Noor acquired a reputation within the British royal family for bringing bad luck to any man who wears it. Since arriving in the country, it has only ever been worn by female members of the family.
Today, the diamond is set in the front of The Queen Mother’s Crown, part of the Crown Jewels of the United Kingdom, and is seen by millions of visitors to the Tower of London each year. The governments of India, Pakistan, Iran and Afghanistan have all tried to claim ownership of the Koh-i-Noor and demanded its return at various points in recent decades. However, the stone’s early history is lost in the mists of time, and the British government insists the gem was obtained legally under the terms of the Treaty of Lahore.
source : Wikipedia