A 29.6-carat blue diamond has been discovered at Cullinan mine in South Africa.

The stone was recovered by Petra Diamonds at its Cullinan mine, about 25 miles north-east of Pretoria.

“This stone is one of the most exceptional stones recovered at Cullinan during Petra’s operation of the mine,” the company said.

Petra Diamonds unearthed a 25.5-carat blue diamond which sold for $16.9 million in 2013.

The latest discovery is also expected to sell for a high price.

“The stone is an outstanding vivid blue with extraordinary saturation, tone and clarity, and has the potential to yield a polished stone of great value and importance,” Petra Diamonds said in a statement on Tuesday.

The 29.6-carat blue diamond has been discovered at Cullinan mine in South Africa

Cullinan mine has produced hundreds of large stones and is famed for its production of blue diamonds – among the rarest and most highly coveted of all diamonds.

The mine was acquired in 2008 by Petra Diamonds, which also operates in Botswana and Tanzania.

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.

Another deep-blue diamond from Cullinan was auctioned for $10.8 million in 2012 and set a world record for the value per carat.

In 1905, the renowned Star of Africa blue diamond – the world’s second largest cut diamond – was discovered at the Cullinan mine. The pear-shaped 530-carat stone was presented to King Edward VII and became part of the British crown jewels.

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