A rare 29.6-carat blue diamond has been discovered at South Africa's Cullinan mine, about 25 miles northeast of Pretoria.
The stone was found by Petra Diamonds, which owns the Cullinan mine that is known to yield hundreds of large stones and is the location of other finds of blue diamonds.
Blue diamonds are among the rarest diamonds on Earth.
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"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 wrote in a statement
Tuesday. "Blue diamonds are among the rarest and most highly coveted of all diamonds and the Cullinan mine is the most important source of blues in the world. This stone is one of the most exceptional stones recovered at Cullinan during Petra's operation of the mine."
Petra found a 25.5-carat blue diamond in 2013, which sold for $16.9 million. The Star of Josephine diamond, found in 2008, was sold for $9.49 million.
"It's very unusual for a diamond of this quality and size to come to market," said Petra spokeswoman Cathy Malins at the time of the 25.5-caret find, the BBC reported
Numis analyst Cailey Barker told Reuters that the new diamond could bring between $15 million and $20 million at auction
Petra Diamond CEO Johan Dippenaar said the new diamond find could be its best in the mine's long history.
"By some margin, this is probably the most significant stone we've ever, in terms of blue stones, recovered," Dippenaar said to Reuters.
Dippenaar said at the company's first-half trading statement that: "The stones in the last year or so are selling well above $2 million per carat. That's not my quote, that's updates in the market."
South Africa is home to three of the 10 richest diamond mines in the world — Venetia, Finsch, and Kimberley. Botswana also has three diamond mines that are also ranked among the world's Top 10.
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