Rough diamonds have their own raw appeal, although they have not fared well in public auctions.

The largest diamond to have been discovered in the past century, the Lesedi la Rona, was unearthed in November last year at Lucara Diamond Corporation’s Karowe mine in Botswana. The uncut 1,109ct stone is the largest rough crystal to have surfaced since 1905, when the 3,106ct Cullinan Diamond was mined in neighbouring South Africa.

Independent reports, including the Gemological Institute of America (GIA) have commented on the
stone’s exceptional quality and transparency. Sotheby’s jewellery division chairman David Bennett called it “the find of a lifetime”, adding that “no rough even remotely of this scale has ever been offered before at public auction”.

Despite all the fanfare, the Lesedi la Rona failed to find a buyer at Sotheby’s London auction in June,when bidding peaked at US$61 million, below the US$70 million reserve price.

Roughs are commonly sold through established channels, including through De Beers or the use of tenders, and rarely through public auctions. David Johnson, midstream communications manager
of The De Beers Group of Companies, says
De Beers sells 90 per cent of its rough diamonds through term contract sales to Sightholder customers, and 10 per cent through online auctions to registered auction customers.

“We are satisfied that we have a very effective sales approach for rough diamonds,” Johnson says.

“It’s a specialised business more or less reserved for professionals of the rough diamond trade,” says Francois Curiel, chairman of Christie’s Asia-Pacific. “If you buy a polished diamond at auction, every dealer and private customer can decide how much he or she wants to pay for it because we know the colour, the clarity, the cut. With a rough diamond, nobody knows.”

You cannot certify a rough diamond. People have tried but it’s impossible.
Roy Cohen, managing director, The Diamond Certification Laboratory of Australia

It is the uncertainty of the yield the Lesedi la Rona would bring that caused the rough to exit the public auction and go back to the more traditional channels of the rough diamond trade. Even stellar reports of the diamond’s potential are still a diamond cutter’s best guess. “It’s an informed guess, but there’s no certainty,” Curiel says.

Roy Cohen, managing director of Sydney-based The Diamond Certification Laboratory of Australia (DCLA), says there is no clear certification process for buying rough diamonds.

“You cannot certify a rough diamond,” he says. “People have tried but it’s impossible.”

Rough diamonds have their own appeal, and many jewellery designers have designed their pieces around rough diamonds, setting the organic shapes of the natural stones in one-of-a-kind jewellery pieces.

Diamond in the Rough is a jewellery house that has found success in working rough diamonds into jewellery pieces. The Iceberg collection showcases octahedron rough diamonds surrounded by pave diamonds to stunning effect.

De Beers put the focus on rough diamonds with the 2015 De Beers Talisman collection
to celebrate its 10th anniversary.

“[We] only [use] the rarest rough diamonds which are naturally beautiful in nature,” says Andrew Coxon, president of De Beers Institute of Diamonds. “Less than one stone in a thousand roughs qualifies.”

Coxon compares the appreciation for rough diamonds to jade, which are judged on their natural beauty and high transparency.

“Chinese jewellery connoisseurs are able to appreciate rough diamonds much in the same way as
with jade, which also does not come with any grading report,” he says.

“Naturally beautiful diamonds of fine patina, form and feel are rarer than beautifully polished diamonds.”