The Gemological Institute of America (GIA) has examined the second largest rough diamond ever recorded, weighing 2,488.32 carats. The examination took place in July 2025 at the GIA laboratory in Gaborone, Botswana.
The diamond, recovered by Lucara Diamond Corporation at the Karowe mine in August 2024, was originally 2,492 carats before minor breakage during cleaning and analysis. Known as ‘Motswedi’—meaning ‘water spring’ in Setswana;the stone was named through a public competition in Botswana. It is surpassed in size only by the 3,106-carat Cullinan diamond discovered in 1905 in South Africa.
Type IIa with no detectable nitrogen
GIA’s analysis confirmed that Motswedi is a single crystal, type IIa diamond with no measurable nitrogen. Dr Wuyi Wang, GIA’s Vice President of Research and Development, stated: “It is the largest known single crystal diamond in existence and undoubtedly formed much deeper within the earth than the majority of diamonds.”
The diamond was assessed by senior GIA personnel including Tom Moses, Executive Vice President and Chief Research and Laboratory Officer, who said: “I have been fortunate to examine many significant, large and very rare diamonds, but I have never seen a gem quality diamond of nearly this size.”
In addition to the main stone, GIA examined 1.50 carats of small fragments that had detached prior to the laboratory assessment.
Gemological structure and potential
Examination revealed the diamond contains several large gem-quality areas with minimal inclusions, indicating potential for high-quality polished stones. No information regarding future cutting or commercial plans has been disclosed.
“Our examinations confirmed that the Motswedi is a single gem-quality crystal, type IIa diamond with no detectable nitrogen,” stated Dr. Wuyi Wang. “It is the largest known single crystal diamond in existence and undoubtedly formed much deeper within the earth than the majority of diamonds.”
Industry significance
Since opening in 2012, the Karowe mine has produced a number of large gem-quality diamonds, reinforcing Botswana’s position in the global diamond sector. The recovery and examination of Motswedi underscores the ongoing output of large stones from the region, which remains an area of interest in the global rough diamond market.
Further technical details are available in an article by Tom Moses and Dr Wuyi Wang on GIA’s website: https://www.gia.edu/gia-news-research/gia-tests-the-motswedi-diamond.
