Gem Diamonds (LON:GEMD) saw prices received for diamonds from its Letšeng mine in Lesotho improve in its fourth quarter.
An average of US$ 2,533 per carat was achieved in the three months to end 2013 compared to US$ 2,022 per carat in the third quarter last year, it said.
"It is pleasing to see the stronger Letšeng diamond prices achieved for the period which were 25% up on the prior quarter," chief executive Clifford Elphick said.
"As mining at Letšeng has moved more into the satellite pipe in Q4 2013, we have seen an expected improvement on the quality of diamonds produced.
"This, together with a strong market saw the final tender of 2013 realise over US$3,000 per carat. This firmer trend in rough prices for Letšeng's high value diamonds looks set to continue into the beginning of 2014," he added.
The firm added that though positive sentiment is expected to continue into the first quarter of 2014, sustained liquidity constraints are expected to mean a cautious approach from most industry participants in both the rough and polished market.
In total, 35 rough diamonds achieved a price of more than US$20,000 per carat during the three months, with 96 stones exceeding that value in the whole year.
Another highlight came in October when a 12.47 carat blue diamond sold for US$7.5 million - a Letšeng record of US$603, 047 per carat.