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Natural Diamond Council Says 41.82-Carat Rough Blue Diamond is an Extremely Rare Discovery January 14, 2026 (0 comments)
New York, NY--Petra Diamonds recently discovered an extremely rare 41.82-carat Type IIb blue rough diamond of seemingly exceptional quality in terms of both color and clarity from the Cullinan Mine in South Africa.
The Cullinan Mine is known for producing some of the world’s most celebrated blue diamonds, including stones that have gone on to set price-per-carat records at international auctions. This latest recovery further underscores Cullinan’s standing as one of the most important sources of rare and exceptional blue diamonds globally.
[Photo credit: Petra Diamonds]
As highlighted in the Natural Diamond Council’s “Fancy Colour Diamonds” report, Type IIb blue diamonds account for only a minute fraction of global diamond production and occupy a singular position within the world of natural gemstones. Believed to form more than 500 kilometers below the Earth’s surface—far deeper than most diamonds—they owe their distinctive blue color to trace amounts of boron, a mineral typically found in seawater. According to the Fancy Color Research Foundation, blue diamonds have been among the strongest-performing color diamonds since 2005 in terms of value, registering a +242% appreciation over the past 20 years.
“On average, around 80% of the value generated by responsible diamond recovery is retained locally, supporting jobs, infrastructure, healthcare, education, and vital social programs, while also contributing significant tax and royalty revenues to national economies,” said Raluca Anghel, head of External Affairs and Industry Relations at the Natural Diamond Council. “Discoveries of this caliber therefore carry profound meaning not only for the global diamond industry, but for the communities and countries that benefit directly and indirectly from their recovery.”
Learn more about the rarity, origins and allure of blue diamonds in the Fancy Colour Diamonds report by the Natural Diamond Council, which explores the geological formation, historic provenance and auction performance of the world’s most exceptional colored diamonds.