The sale of rough diamonds at Botswana's Debswana Diamond Co declined 17% between January and June this year, according to data published by the Bank of Botswana, amid market weakness reinforced by global macroeconomic uncertainty.

Debswana is a joint venture of Botswana and Anglo-American Plc's AAL.L unit De Beers, and as it stands, sells 75% of its output to De Beers, with the remainder taken up by state-owned Okavango Diamond Co, Reuters news agency reports. 

At the end of June, Botswana and De Beers reached a new diamond sales deal. This agreement involves Botswana – the world's largest diamond producer by value – to gradually increase the share of rough stones it acquires from the joint venture over the coming ten years to 50%.

During the first six months of the year, Debswana sold diamonds worth $2.179 billion compared to $2.622 billion between January and June last year, according to a statement by the central bank earlier this week.

In terms of the Botswana Pula, the rough sales registered an 8% decline to 28.621 billion Pula. The data from the Bank of Botswana showed the local currency depreciated 8.4% against the Dollar in the 12 months to June, the Reuters report goes on to add.

Debswana, having produced 12.7 million carats in the first six months of the year, makes up almost all the diamonds produced in the African country. Furthermore, the Lucara Diamond Corp's LUC.TO Karowe mine is the only other operating diamond mine in Botswana.