Leading diamond company De Beers announced record first-half rough diamond sales of $3.5bn (£2.1bn) in the six months to June. Sales were 33 per cent higher than in the first half of 2010, "driven by exceptional price growth, powered by strong demand for diamonds in the US, China and India".

De Beers' estimate that rough diamond prices appreciated by some 35 per cent during the first half capped a series of positive updates from the sector. In its first-half trading update, Petra Diamonds reported increased sales of 24 per cent, despite a slight decrease in production in the period. Adjusting for the $35m contribution of the Cullinan Heritage stone to the corresponding period last year, sales would have increased by 55 per cent.

Stellar Diamonds previously reported that the first parcel of stones exported from its Tongo kimberlite dyke project in eastern Sierra Leone had been valued at $191 per carat, despite not containing any large stones. Earlier in July, Firestone Diamonds announced excellent results from its second tender of the year. The company sold 14,248 carats for gross proceeds of approximately $2m, which represents an increase in value of 42 per cent from April.

De Beers expects the strong consumer demand seen in the first six months to continue through the remainder of the year. In its quarterly review of the sector, Charles Stanley Securities calculated that despite the strong price environment, rough diamond markets softened slightly in June as the Kimberley Process (which certifies the origin of stones as conflict-free) looked set to approve production from Marange in Zimbabwe, despite opposition from the US and Europe.

In conclusion, however, the broker expects rough prices to strengthen again in the final quarter after pausing for breath in the third quarter, and says this would support its thesis of a long-term bull market for diamonds.