Diamond production at its Murowa mine in Zimbabwe rose marginally to 279,000 carats during the first nine months of the year from 277,000 carats mined in the corresponding period last year, according to global mining giant Rio Tinto which operates the mine through a subsidiary company.

Located near Zvishavane in Zimbabwe's Midlands Province, Murowa is a 78-22 per cent partnership between Rio Tinto and RioZim Limited (RioZim), an independent Zimbabwean-owned and listed company. It is one of six diamond mines operating in Zimbabwe.

Output at the mine for the third quarter which ended on Sept 30 this year declined to 90,000 carats from 119,000 carats mined in the same period last year. Overally, diamond output for the group during the third quarter 2013 increased as a result of the upgrade of underground mining.

"Diamonds recovered in the third quarter are seven per cent higher than in the previous quarter of 2013 due to ramp up of underground mining and higher grades recovered," Rio Tinto said.

Meanwhile, Rio Tinto said total share of production for the group during the first nine months reached 11,529,000 carats compared with 9,873,000 carats mined in the same period in 2012.

Output at the company's Argyle mine in Australia increased by 27 per cent to reach 8,205,000 carats while production at its 60 per cent owned Diavik mine in Canada dropped 3.0 per cent to 3,106,000 carats.

Rio Tinto chief executive Sam Walsh said the group had achieved positive results. "We maintained good progress against our strategic priorities to improve the performance of our businesses, strengthen the balance sheet and deliver our approved growth projects. We are also making further important gains in productivity across our operations and continue to drive costs out of the business," he said.

Rio Tinto, which had considered divesting from the diamond business, expects to mine 15.7 million carats of diamonds in 2013 compared with 13.122 million carats recovered in 2012.

The diamond industry is currently going through a lean spell mainly because of the Euro zone debt crisis coupled with slowing Asian purchases while demand for end products continues to decline. This resulted in rough diamond prices slumping 16 per cent last year with the gem market growing by about 3.0 to 4.0 per cent compared with growth of 10 per cent in 2011 while in 2013 it is expected to register marginal growth again.

Industry experts, however, expect a rebound in prices this year following an announcement by De Beers, the world's largest diamond producer, late last year that it was going to constrain supply in 2013.