THE WORLD'S LARGEST DIAMOND Most highly-prized of all precious stones, diamonds consist of pure crystalized carbon. One of the chief sources is the South African mines - steeply-walled volcanic "pipes" filled with broken-up masses of bluish -green rock known as "blue ground". The famous Cullinan stone, discovered near Pretoria in 1905 and presented to King Edward VII in 1907, was the size of a turkey's egg and weighed in its uncut state 3,025 carats. From it were cut nine large diamonds (now part of the Crown Jewels) and 96 small brillants. We illustrate the stone in the rough, and also the largest of the cut diamonds, mounted in the Royal Sceptre.