An exceptional 122.52-carat blue diamond discovered at the Cullinan mine in South Africa could fetch a record price, an analyst with UK broker FinnCap told The Telegraph last week.
London-listed Petra Diamonds, the owner of the Cullinan mine outside Pretoria, announced last Friday that it had unearthed the diamond, saying in a statement that "the rarity of a blue diamond of this magnitude sets it apart as a truly significant find".
Blue diamonds are more valuable than their white counterparts, and both, once cut, are worth more than their rough (uncut) originals.
Petra said the stone "will require further analysis in order to assess its potential value, and upon completion of this process, Petra will be in a position to evaluate its optimal route to market".
Martin Potts, a mining analyst at FinnCap, told the Telegraph: "So far, the highest price on record paid for a rough [uncut] diamond was £20-million [US$35.3-million], in February 2010 for a 507-carat white stone, also recovered from Cullinan. We think that this stone may break that record."
It is the largest blue diamond the company has recovered since its 2008 acquisition of Cullinan, one of the world's most celebrated diamond mines.
Located at the foothills of the Magaliesberg mountain range, 37 kilometres north-east of Pretoria, the Cullinan mine earned its place in history in 1905 with the discovery of the Cullinan diamond, the largest rough gem diamond ever found at 3 106 carats.
This iconic stone was cut into the two most important diamonds that form part of the Crown Jewels in the Tower of London - the First Star of Africa, which is mounted at the top of the Sovereign's Sceptre and which at 530 carats is the largest flawless cut diamond in the world, and the Second Star of Africa, a 317-carat polished diamond which forms the centrepiece of the Imperial State Crown.
According to Petra Diamonds, the Cullinan mine frequently yields diamonds larger than 10 carats, and has produced over 750 stones weighing more than 100 carats, 130 stones weighing more than 200 carats, and around a quarter of all diamonds weighing more than 400 carats.
"Cullinan is also renowned as the world's most important source of blue diamonds, providing the collection of 11 rare blues displayed in 2000 at London's Millennium Dome alongside the Millennium Star and which included the fancy vivid blue 'Heart of Eternity' (27 carats polished)," the company said.
Cullinan's previous major yield, a 29.6-carat blue diamond found in January, sold the following month for $25.6-million.
Petra Diamonds has interests in five producing mines in South Africa and one in Tanzania, and also maintains an exploration programme in Botswana.