<P> The Cullinan Diamond is the largest gem - quality rough diamond ever found, weighing 3,106.75 carats (621.35 g), discovered at the Premier No. 2 mine in Cullinan, South Africa, on 26 January 1905 . It was named after Thomas Cullinan, the mine's chairman . </P> <P> In April 1905, the Cullinan was put on sale in London, but despite considerable interest, it was still unsold after two years . In 1907 the Transvaal Colony government bought the Cullinan and presented it to King Edward VII on his 66th birthday . </P> <P> Cullinan produced stones of various cuts and sizes, the largest of which is named Cullinan I or the Great Star of Africa, and at 530.4 carats (106.08 g) it is the largest clear cut diamond in the world . Cullinan I is mounted in the head of the Sovereign's Sceptre with Cross . The second - largest is Cullinan II or the Second Star of Africa, weighing 317.4 carats (63.48 g), mounted in the Imperial State Crown . Both diamonds are part of the Crown Jewels of the United Kingdom . </P> <P> Seven other major diamonds, weighing a total of 208.29 carats (41.66 g), are privately owned by Queen Elizabeth II, who inherited them from her grandmother, Queen Mary, in 1953 . The Queen also owns minor brilliants and a set of unpolished fragments . </P>

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