South African mine unearths rare blue diamond shaped like Africa worth $40 million

A rare blue diamond weighing almost 42 carats has been unearthed in South Africa’s historic Cullinan Mine, with industry experts suggesting it could fetch in the region of $40 million at auction.

• A rare blue diamond weighing nearly 42 carats has been discovered at South Africa’s Cullinan Mine.
• Experts say the stone could fetch up to $40 million when it eventually goes to auction.
• The gem belongs to the ultra-rare type IIb category, accounting for less than 0.1 per cent of natural diamonds.
• The discovery comes as global diamond prices face pressure from lab-grown alternatives and weaker demand.

The discovery reinforces the mine’s reputation as a source of some of the world’s most exceptional coloured diamonds.

Petra Diamonds, which operates the site about 20 miles east of Pretoria, described the find as a “41.82 carat type IIb blue diamond of seemingly exceptional quality in terms of both its colour and clarity”.

The company said specialists are still analysing the rough stone to determine the optimal cutting and sale strategy.

Type IIb diamonds are among the rarest in nature, comprising less than one-tenth of one percent of all diamonds.

Their distinctive blue hue comes from trace amounts of boron deep within the earth, and they form at extreme depths before volcanic activity brings them closer to the surface.

The Cullinan Mine holds a special place in gem lore. It was the source of the legendary Cullinan Diamond, discovered in 1905, the largest gem-quality rough diamond ever found. That historic stone was cut into nine major gems, several of which are now part of the British Crown Jewels.

Johannesburg diamond dealer Gregory Katz, speaking to News24, said the latest find could command between $30 million and $40 million once final cutting and polishing decisions are made.

He explained that cutters will try to maximise the finished size, but “the finished, polished stone would be significantly smaller than the original rough diamond”.

“There is little doubt it is a significant find,” Katz added, underlining the rarity and potential market value of such stones.

The announcement comes at a challenging time for the diamond industry, as global diamond prices have been under pressure in recent years due to a surge in consumer spending during the pandemic and the rapid rise of lab-grown alternatives, which are typically cheaper than natural gems.

The latest discovery is likely to draw renewed interest from collectors and investors alike, particularly in African and global luxury markets.

Petra Diamonds has not yet confirmed when the stone will go to market, but industry watchers will be closely tracking developments.