Diamond sales at De Beers dropped off in the first part of the year as the group faced slowing demand for its smaller products.
Sales dropped by around 25 per cent in the initial so-called cycle of 2018, a reduction of $167m to $505m.
The figures also showed a slowdown from the final cycle of 2018, when the company sold $544m of the stones.
De Beers splits the year into ten part, or cycles, to report sales.
“Rough diamond sales during the first sales cycle of 2019 were lower than those for the equivalent period last year, reflecting higher than normal sales in the previous cycle and the slow movement of lower value rough diamonds through the pipeline,” said chief executive Bruce Cleaver.
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The news comes less than a week after the Anglo-American owned diamond producer said it had increased 2018 production to 35.3m carats, a six per cent increase, as output grew at its Orapa mine.
It set production guidance for 2019 down slightly from last year, at between 31m and 33m carats.