In mid-January, one of the largest diamonds ever discovered was unearthed at a mine in Africa. The 910-carat diamond was pulled from the Letseng mine in Lesotho, and is believed to be the fifth largest gem-quality diamond ever recovered. London-based Gem Diamonds Limited has owned the Letseng mine since 2006, and in that time has produced several massive rough diamonds, weighing 493 carats, 550 carats, and 603 carats, the last of which sold for $12.4 million.
This recent discovery, however, is the most impressive the Letseng mine has produced. The stone is roughly the size of two golf balls. There are already estimates it could be worth as much as $40 million, Bloomberg reports.
The 910-carat diamond weighs 6.4 ounces—more than a baseball—and has been identified as a Type IIa. A diamond’s Type refers to its chemical composition, and a Type IIa means the diamond is almost pure carbon, with no measurable traces of nitrogen or boron. Type IIa diamonds are exceedingly rare, representing only 1 to 2% of all mined diamonds in the world. They are of such high quality, and unearthed so infrequently, that they command up to a 15% pricing premium when they can be found.
The 4 C Quality Grades
So how will this glittering behemoth be graded in terms of the 4 Cs we all know and love? So far, the 910-carat rough diamond has been identified as a D color, the best possible color grade for a white diamond. Incredibly, it has no discernable traces of yellow or brown hues even under 10X magnification.
Other details of quality and aesthetics — shape, cut grade, clarity grade and final carat weight — will be measured once the diamond has been cut and polished. There are unique challenges in cutting such a large stone. The goal when cutting any diamond is to remove inclusions and minimize waste while maximizing brilliance and carat weight. In the case of this piece of rough, an expert gemologist will likely spend weeks or even months analyzing the rough diamond to decide on the optimal angles to cut. The rough will then be sent to a highly skilled diamond cutter to begin the process of turning the rough diamond into a glittering masterpiece.
Incredibly, despite its size, this discovery is not the biggest rough diamond on record. The largest piece of rough diamond ever mined was over 3,000 carats, unearthed in South Africa in 1905. The largest cut diamond is the King of Thailand’s Golden Jubilee, which started as a 755.5-carat rough diamond and ended up as 545 carats once cut.
Want to read more about the world’s largest and most valuable diamonds? Start here!