News of the unusually sharp increases spread swiftly through the community of 80-odd handpicked De Beers customers, according to people familiar with the discussions. But what followed was even more remarkable: within hours, some of those same stones were trading hands at a further 10% markup, as buyers who have access to De Beers flipped them to traders and manufacturers that don't. 

The spiking prices -- and buyers' willingness to pay them -- are the latest sign of roaring demand in the secretive rough-diamond trade. Just nine months ago, the industry had been brought to a standstill by the pandemic. Now, the cutters and polishers who form the backbone of the global diamond market are competing fiercely for stones.