The Largest Uncut Diamond Ever Discovered
The biggest uncut diamond in the world is the Sergio, a black diamond weighing 3,167 carats, making it the heaviest rough diamond ever recovered. It was discovered in 1895 in the Lençóis region of Bahia, Brazil, and remains the largest uncut gem-quality diamond on record according to mineralogical surveys and historical gem databases diamond records Forbes.
Unlike most large diamonds that are cut into polished stones, the Sergio has remained uncut, preserving its original rough form. Its black color and carbonado structure make it a rare type of diamond, distinct from the clear crystalline stones typically associated with major gem finds. The stone's sheer mass and unusual composition have kept it a subject of study in mineralogy and gem science.
Comparison With Other Major Rough Diamonds
The Sergio surpasses other famous large rough diamonds such as the Cullinan, which weighed 3,106 carats before being cut, and the Lesedi La Rona, a 1,109-carat stone recovered in Botswana in 2015. While the Cullinan produced several polished gems for the British Crown Jewels, the Sergio has never been faceted or shaped Smithsonian diamond history.
Rankings of the largest rough diamonds consistently place the Sergio at the top by total carat weight, followed by the Cullinan and then the Lesedi La Rona. These stones are often cited in industry reports by companies like De Beers and Rio Tinto when discussing extraordinary gem discoveries and the economics of rough diamond supply chains De Beers SEC filing rough diamond stats.
Current Status and Ownership
The Sergio diamond is held in a private collection, and its exact current owner has not been publicly disclosed in recent authoritative sources. The stone has changed hands several times since its discovery, but its status as the largest uncut diamond remains undisputed in gemological references and auction house records Forbes diamond value analysis.
Large uncut stones like the Sergio are valued not only for their rarity but also for their potential to yield exceptionally large polished gems if cut. However, the decision to leave it uncut reflects both its scientific importance and the practical challenges of cutting a stone of such irregular and dense structure. Its continued existence provides a benchmark for evaluating future diamond discoveries worldwide.