The Great Big Diamond Boom

(The Economist) - Earlier this year a diamond the size of a tennis ball went up for sale at Sotheby’s. At 1,109 carats, the Lesedi La Rona is not just 500 times bigger than even the ritziest of engagement rings, it is the largest diamond found since the discovery of the Cullinan (3,106.75 carats) in 1905. More remarkable still is the streak of large-diamond discoveries over the past few decades: by one reckoning about as many supersize diamonds (those that weigh 200 carats or more) have been unearthed in the past two decades as were found in the rest of the 20th century. Moreover, this streak seems to be growing hotter. Miners are getting better at locating and preserving big diamonds. Now, with the aid of faster computers, sorting machines can use X-rays to scan tons of rock being carried on conveyor belts towards the crushers and instantly analyse the molecular composition of each boulder. When a diamond is spotted, the machine immediately diverts it and saves it from oblivion.