The rare stone was recovered by Petra Diamonds at its Cullinan mine, located to the north-east of Pretoria, which is famed for its production of blue diamonds.
Experts believe that the diamond could be worth more than $10 million. Similar finds at the mine in recent years have commanded similarly high prices and the news of the latest discovery has resulted in Petra Diamond’s share price rising.
A similar 26.6-carat blue rough diamond discovered by the company in May 2009 was cut into a near perfect stone and fetched just under $10 million at a Sotheby's auction, while another deep-blue diamond from Cullinan was auctioned for $10.8m last year and set a world record for the value per carat.
"It's very unusual for a diamond of this quality and size to come to market," said company spokeswoman Cathy Malins.
Arguably the most famous of discoveries to originate from the Cullinan mine was made in 1905, when the 530-carat stone called the Star of Africa was brought up to the surface. To this day it remains the world’s second largest cut diamond and went on to become part of the British crown jewels.
