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Researcher says diamond miners to reconsider their treatment of low-carat kimberlites, claiming they could bring big diamond surprises
Diamond crystal South Africa
Credit: Matteo Chinellato /

Florida International University research professor Stephen Haggerty, who recently attended the 11th International Kimberlite Conference in Botswana, urges diamond miners to reconsider their treatment of low-carat kimberlites, claiming they could bring big diamond surprises.


The Big Diamonds Coming from Low Pipes


In an interview with Mining Weekly following the conference, Haggerty claims that these pipes have the propensity to host big Type II diamonds that sell for large sums of money. He explains that while De Beers walked away from what is today the Karowe mine in Botswana, as well as what is today the Letseng mine in Lesotho, “each asset has yielded very large high-value diamonds on becoming operational”.


Haggerty added that, as everyone in the industry now knows, the large diamonds sold from Karowe have ranged in price from $20 to $63 million per diamond, not counting the tennis-ball-sized 1,109 carat diamond, the third-largest diamond after the celebrated Cullinan and the Excelsior diamonds, which Karowe’s owner, Lucara, sold to Graff for $53 million. The huge diamond, named “Lesedi La Rona” was discovered by Lucara in Botswana in November 2015. It is the largest gem-quality rough diamond to have been discovered in over a century, and the largest gem-quality diamond in existence today.


De Beers sold the Karowe property because the grades were considered to be too low and did the same at Letseng, which is also producing big diamonds. However, Haggerty told Mining Weekly, “That’s where the big diamonds are, that’s where the diamonds of value are”.


Haggerty goes on to explain that these big Type II diamonds “were formed in the presence of metallic iron in the lower mantle at depths greater than 660 km below surface, where they resided for 2.8 billion to 3 billion years before being elevated”.


Haggerty is one of eight to have attended all eleven of the international kimberlite conferences, the first of which was held in South Africa in 1973.

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