The 507.6-carat stone, weighing more than 100 grams was found at the Cullinan mine near Pretoria and is approximately worth 12 million pounds.
This stone is one among the 20 high quality rough diamonds ever discovered.
Alongside this exceptional gem, the miners found other valuable gems including one diamond of 168.00 carats and two other stones of 58.50 and 53.30 carats.
And according to experts these three stones would be worth up to seven million pounds.
The world"s biggest certified diamond was also found at the very same Cullinan Mine. This 3,106-carat Cullinan gem was unearthed in 1905.