The reasons behind the big diamond finds

I feel as though I’ve written a fair number of “large rough unearthed” stories in recent months, so many, in fact, that I began to wonder: Has this been an unusually active year for finding rough diamonds that are 100 carats or larger?

Michelle Graff michelle.graff@nationaljeweler.com

The two largest, publicized finds to date in 2014 belong to Vancouver-based Lucara Diamond Corp.: a 259-carat piece of rough and a 239-carat piece of rough, both found at the company’s Karowe mine in Botswana.

These two huge finds were part of a larger haul the diamond company removed from Karowe in the second quarter, a bounty that included 13 diamonds larger than 100 carats, eight of which were gem-quality. In addition to these two 200-carat-plus diamonds, the company found two rough diamonds weighing 153 carats each and a 133-carat stone.

The third biggest gem-quality rough find of the year was a very recent one: Gem Diamonds Ltd. discovered a 198-carat “exceptional white” Type IIa rough diamond (pictured above) late last month at its Letšeng mine in Lesotho, a small nation entirely enveloped within South Africa. The rarest type of diamond on earth, Type IIa’s contain no measurable nitrogen or boron impurities, and colorless Type IIa stones are known for their exceptional color and clarity.

The discovery of this 198-carat piece of rough comes in addition to Gem’s unearthing of a 162.06-carat Type IIa diamond and a 161.74-carat Type I stone earlier this year, also at Letšeng.

And, of course, I cannot omit the 122.52-carat piece of blue rough (pictured below) Petra Diamonds Ltd. pulled out of the Cullinan mine in South Africa, a stone that could set a new world record price for a rough diamond when it’s sold.

Given all of these large rough finds, which are sure to yield some exceptional polished diamonds, I asked Martin Potts, research director for mining at London-based financial advisory firm finnCap, if, comparatively speaking, 2014 has been a year in which miners have found an unusually high number of large rough diamonds.

He said “probably yes,” and it is mostly due to the Karowe mine. Fully commissioned by the second quarter of 2012, the mine has proved to be a consistent supplier of large stones, which was not necessarily expected to be the case when the mine was built.

Also contributing to the wealth of big diamonds coming up is the fact that Gem Diamonds is mining in Letšeng’s satellite pipe again, which historically has been the source of most of the mine’s large stones, Potts said.

And, as Russell Shor, a senior industry analyst with the Gemological Institute of America, points out, it is a mine with quite a history.

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While the 198-carat diamond is the largest stone to emerge from the mine this year--and actually the largest since 2011, according to Potts--this also is the mine that produced the 603-carat Lesotho Promise, the 15th largest diamond ever found; the 493-carat Letšeng Legacy; a 553-carat diamond in 2011; and a 478-carat diamond in 2008.

“The latest find,” Shor observes, “is not unusual for this particular mine.”

He adds that the Cullinan mine, which produced the 122.52-carat blue stone this year that could shatter the world rough diamond price record, also historically has been a prolific source of significant stones.

It is the source of one-fourth of all diamonds more than 100 carats in size, including the largest rough diamond discovered to date: a 3,106-carat piece of rough aptly named the Cullinan diamond.

Michelle Graffis the editor-in-chief at National Jeweler, directing the publication’s coverage both online and in print.

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