The Type-IIa stone, just smaller than a tennis ball, is the largest diamond discovery for more than 100 years, according to Vancouver-based Lucara. It was recovered by machines at the south lobe of Karowe mine in central Botswana.
"It is almost impossible to estimate a value for such an extraordinary stone given that a valuation is highly dependent on the color, clarity and cutting and polishing characteristics," Edward Sterck, a London-based analyst at BMO Capital Markets, wrote in a note Thursday.
Lucara sold a 341.9-carat Type-IIa diamond in July for $20.6 million, or $60,000 a carat, Sterck said. The company’s shares jumped as much as 37 percent in Toronto trading, the steepest intraday gain since 2008.
The value of the find and who will want to buy it will depend on the size and quality of the polished stones that can be cut from it. While Lucara will likely sell it at a tender in Botswana, the cutting, polishing and eventual sale to a final owner may take many years. Antwerp and New York are the leading cutting centers for exceptional gems.