Gemological Institute of America (GIA) has examined the 2,488.32-carat Motswedi diamond, the world’s second largest gem-quality rough, at its laboratory in Gaborone, Botswana.
Recovered in August 2024 from Lucara Diamond Corporation’s Karowe mine, the diamond originally weighed 2,492 carats. Named Motswedi—meaning “water spring” in Setswana—through a national competition, the stone is second in size only to the 3,106-carat Cullinan diamond discovered in South Africa in 1905.
“This is undoubtedly a diamond of great historical importance,” said Tom Moses, GIA Executive Vice President and Chief Laboratory and Research Officer. “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.”
Examinations by Moses and Dr. Wuyi Wang, GIA Vice President of Research and Development, confirmed that Motswedi is a single, type IIa gem-quality crystal with no detectable nitrogen. “It is the largest known single-crystal diamond in existence and undoubtedly formed much deeper within the earth than the majority of diamonds,” Dr. Wang explained.
The GIA team also studied 1.50 carats of fragments that separated during cleaning, accounting for the slight weight difference since recovery. Tests revealed the rough contains several large, high-quality “blocks” with minimal inclusions, making it an extraordinary specimen.