Largest diamond, the Cullinan, ever found was discovered in the Premier Diamond Mining Company in Cullinan, South Africa in 1905. The stone, named after Sir Thomas Cullinan (owner of the mine), was 3,106 carats. The rough diamond was cut into seven very large gems and 96 smaller gems. Many of the larger gems are in the crown jewels of the United Kingdom. Idea: Have children illustrate how diamonds are made and how they are cut by visiting: Diamonds.