Most expensive blue diamond South Africa
Image: Petra Diamonds Limited
  • A UK-based mining firm recovered a 39.34 carat type IIb blue diamond from South Africa's Cullinan Mine in April.
  • The rare diamond is now being sold to the highest bidder, with viewings in Antwerp, Dubai, Hong Kong, and New York.
  • A similar diamond, the 29-carat Blue Moon of Josephine, sold for around R352 million in 2015.
  • A year later, once cut, polished, and mounted, the diamond fetched R666 million and broke the record for the highest price per carat ever paid for a gem at auction.

A rare blue diamond recovered at the iconic Cullinan Diamond Mine in South Africa will go to auction in July. A similar rough gem – the 29-carat Blue Moon of Josephine – sold for $25.6 million (R352 million at current exchange rates) in 2014.

Petra Diamonds announced in April that it had recovered a 39.34 carat type IIb blue diamond at the Cullinan Mine. For more than a century, the Cullinan Mine, situated at the foothills of the Magaliesberg mountain range, 37 kilometres north-east of Tshwane, has produced the world's most famed diamond finds.

The rough diamond recently discovered by Petra, which purchased the celebrated mine from De Beers in 2007, is described as a gem of "exceptional quality in terms of both its colour and clarity". Petra Diamonds announced on Tuesday that the type IIb blue diamond would open to viewings in Antwerp, Dubai, Hong Kong, and New York this month.

Interested buyers will have until 12 July to place their highest bids.

Petra has not set a price range for this particular gem but instead pointed to recent sales of similar blue diamonds. The UK-based mining group, which has three underground operations in South Africa, defines these diamonds as "very rare".

The Blue Moon of Josephine, which was also recovered from the Cullinan Mine, was cut and polished to a 12-carat gem. The mounted type IIb blue diamond went on to sell for $48.4 million (R666 million at the current exchange rate) in 2015, setting a new world record for the highest price per carat ever paid for a gem at auction.

"Type IIb blue diamonds are so rare that their age has not been established," noted Petra.

"The boron that gives their blue colour has been linked to seawater suggesting that these diamonds are a record of rocks from the ocean floor that have been transported to the lower mantle by plate tectonics, where these diamonds formed under conditions of extreme pressure and temperature."

Type II diamonds have no nitrogen "impurities" and are rarer, larger, and harder than type I diamonds. Type IIa diamonds, which represent 1% to 2% of all the world's natural diamonds, have been recovered in India and Australia and have vivid yellow, brown, orange, pink, purple, and red tones.

Type IIb diamonds are the rarest of all the classes, accounting for just 0.1% of the world's natural diamonds. Other blue diamonds extracted from the Cullinan Mine over the last decade by Petra include:

  • The Cullinan Dream (122 carat rough blue diamond) sold for $25.3 million (R348 million) in 2016.
  • A 20.08 carat Type IIb blue diamond sold for $14.9 million (R205 million) in November 2019.
  • The Letlapa Tala Collection of five blue diamonds, weighing 85.6 carats in total, sold as a suite of stones for $40.36 million (R556 million) in November 2020.

The Blue Moon of Josephine was overtaken as the most expensive jewel ever sold at auction by the rectangular 14.6 carat Oppenheimer Blue diamond which fetched $57.5 Million (R792 million) in 2016. The Oppenheimer Blue was dethroned a year later by the 59.6 carat Pink Star diamond which sold for $71 million (R977 million).

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