Botswana posted a 41 percent fall in exports of rough diamonds to $531.9 million in the third quarter of 2015 due to low sales at De Beers sights in recent months.
With zero exports in July, the figure for August was $358.5 million and September exports were $173.4 million, according to the Bank of Botswana.
In the first nine months of this year, exports dropped 23 percent on the year to $2.3 billion.
Most of the country's exports are diamonds mined by Debswana, the joint venture between Botswana and De Beers, which saw a decline of 35 percent to 4.074 million carats in the third quarter of 2015.
The miner's output in the Jan-Sept period dropped 15 percent to 15.6 million carats, De Beers said. De Beers’ overall production for the period fell 11 percent to 21.6 million carats.
De Beers' sightholders were allowed to reject about half of their allocated supply of rough diamonds in the October sight and can defer their November allocations to December.