The Cullinan Diamond is the largest rough diamond ever discovered. The giant gem was discovered in 1905 in a mine founded by Thomas Cullinan, the diamond originally weighed 3,106 carats. The diamond yielded hundreds of individual gemstones, including the 530-carat Great Star of Africa.

In September 2009, the diamond mining group Petra Diamonds discovered a 507.55 carat white diamond at a mine in South Africa. This mine is the same one where the Cullinan Diamond was found.http://www.google.com/hostednews/afp/article/ALeqM5jg4TsFRoB2N0YjVlD_K8CYOCrzMg

While the Cullinan Diamond was the largest rough diamond ever discovered, it did not yield the largest round stones. After the diamond was split in 1908 by master diamond-cutter Joseph Asscher, many of the resulting gems became part of the British Crown Jewels, housed in the Tower of London. The Great Star of Africa became the headstone of the Scepter with the Cross, the prize of the Crown Jewel collection. A diamond discovered in Lesotho in early September 2008 was a rough cut diamond weighing 478 carats; that diamond is expected to yield a world record round stone of at least 150 carats. The current round stone diamond record is held by the fabled Koh-i-Noor Diamond, which weighs 105 carats.