198-carat rough diamond surfaces in Lesotho

London--Gem Diamonds Ltd. made its largest gem-quality rough diamond find to date this year when it pulled a 198-carat piece of rough from its Letšeng mine in the Kingdom of Lesotho last month, the latest in a line of 100-carat-plus stones found this year.

Roughly the size of a large strawberry, the stone is a Type IIa diamond and is described by Gem Diamonds as an “exceptional white, high-quality diamond (that) displays no florescence.” A spokeswoman for the mining company said they cannot comment on what size of polished diamond the stone will yield nor the estimated price it will fetch.

However, Martin Potts, a mining analyst with London-based financial advisory firm finnCap, told National Jeweler that he has seen a photo of the stone and, even prior to cleaning, it looks “good.” He estimates the stone will sell for $12 million to $15 million.

He adds that it is the third largest rough diamond declared this year, topped only by the 258.69-carat stone Lucara Diamond Corp. sold in July from the Karowe Mine in Botswana and the 239-carat stone it is offering in its next tender. In addition, the 198-carat white diamond is the largest gem-quality stone to emerge from Letšeng since August 2011, when the mining company found a 553-carat rough diamond, Potts said.

The unearthing of this exceptional piece of rough is one of a number of diamonds larger than 100 carats found in 2014.

In addition to the two diamonds noted above, Gem Diamonds found a 162.06-carat Type IIa diamond and a 161.74-carat Type I stone earlier this year, also at Letšeng.

Petra Diamonds Ltd. discovered an exceptional 122.52-carat piece of blue rough at the Cullinan mine in South Africa in late spring, and Potts told Reuters at the time that this stone could set a new world record price for a rough diamond. A 507-carat white diamond sold for $35.3 million in February 2010 is the current rough world-record holder.   

In addition to these four 100-carat-plus stones, Lucapa Diamond Co. announced in January that it found a 95.45-carat Type IIa diamond at its Lulo Diamond Concession in Angola.

Gem Diamonds bought Letšeng in 2006 and since that time the mine has produced of the 20 largest white gem-quality diamonds ever found. Commenting on this latest find, Gem Diamonds CEO Clifford Elphick said “The recovery of this large, high-quality white diamond