Diamonds that made history.

The largest gem-quality rough diamond ever found was recovered near Pretoria, South Africa, in 1905 and weighed 3,106 carats. It was named after Thomas Cullinan, chairman of the mining company, and presented to King Edward VII in 1907.

The stone was cut in Amsterdam by the Asscher firm in 1908 and yielded nine major diamonds. The largest, Cullinan I at 530.2 carats, sits in the Sovereign's Sceptre with Cross. Cullinan II is set in the Imperial State Crown.

Probably from the Golconda mines of central India, the Koh-i-Noor passed between Mughal emperors, Persian shahs, Afghan rulers and the Sikh court before the East India Company took it in 1849 under the Treaty of Lahore and it was surrendered to Queen Victoria.

In 1852 it was recut from about 186 carats to 105.6 carats to suit European taste for brilliance. It was set in the Crown of Queen Elizabeth The Queen Mother in 1937. Its ownership remains contested, and it is now presented at the Tower of London as a symbol of conquest.

Found in India at the beginning of the eighteenth century, this diamond was bought by Thomas Pitt, governor of Madras, and cut in London to about 140 carats. In 1717 it was sold to Philippe d'Orléans, Regent of France, whose title it carries.

It was set in the coronation crown of Louis XV, later in the hilt of Napoleon's sword, and has been displayed at the Louvre since 1887 among the surviving French Crown Jewels.

Famous diamonds are exceptional in size, but the questions they raise are the same for any stone. Where did it come from, and can that be documented? Who cut it, and how well? What has been done to it since? A grading report answers some of this; the stone itself, in your hand, answers the rest.

Names and legends add romance, not quality. The quality is in the light.