Editor’s Note
This article details the extraordinary discovery of a 41.82-carat natural blue diamond at South Africa’s Cullinan Mine, a find of immense rarity and potential value. The piece explores its significance for the gem market and the local community.
Recovered from South Africa’s legendary Cullinan Mine, the 41.82-carat natural blue diamond ranks among the rarest finds on Earth, and it will have a major impact on the local community.
By Grant Mobley, Published: January 14, 2026
Petra Diamonds has just announced the discovery of an almost unbelievable 41.82-carat natural blue diamond from the legendary Cullinan Mine in South Africa. Early images and information from Petra suggest it is of exceptional color and clarity, placing this stone squarely among the most important blue diamond discoveries of all time.
Blue diamonds already occupy the rarest tier of natural gemstones. A blue diamond of this size, recovered from one of the world’s most storied mines, immediately invites comparison to some of the most valuable diamonds ever sold. Yet, for all the excitement surrounding the find, some of the most important chapters of this diamond’s story have not been written yet.
Below is what to know about this incredible new blue diamond discovery.
This natural diamond belongs to the ultra-rare classification of Type IIb diamonds, which means that it contains trace amounts of boron and little to no nitrogen. In a natural diamond, boron changes everything. Boron alters the way light moves through the diamond, absorbing red, orange, and yellow wavelengths and producing the blue and grayish-blue tones collectors prize.
Type IIb diamonds account for only about 0.1 percent of all natural diamonds, according to the GIA. This makes them among the rarest materials found in nature. Most of the world’s famous blue diamonds fall into this category, and their scarcity places them at the very top of the diamond market. Some Type IIb diamonds even conduct electricity, which is a scientific curiosity that makes them even more fascinating.
Cullinan Mine holds a singular position in diamond history. Discovered in 1902, the mine produced the 3,106-carat Cullinan Diamond, the largest gem-quality diamond ever found, later cut into nine principal stones that now reside in the British Crown Jewels. Beyond its colorless treasures, Cullinan has also earned recognition as the world’s most important source of natural blue diamonds.
Two Cullinan discoveries define the modern benchmark for blue diamond value:
