Miner Petra Diamonds said it ramped-up production and boosted revenues in the final six months of last year.
The FTSE 250 business said production jumped by 24% to 2.01m carats in the half year to the end of December compared to a year ago. It added sales rocketed by 48% to $228.5m (£184m, €213m) in the period.
The group, which runs diamond mines in South Africa and Tanzania, said it was on track to hit its full-year production target of 4.4m-4.6m carats.
It said it was seeing "some evidence of improving retail demand, with certain jewellery retailers reporting slight growth in sales for the 2016 festive period".
The group added it was also seeing "steady demand" in the rough diamond market, expected in lower value categories in India, due to the sudden withdrawal of high-value notes from circulation by the government last year.
It said small firms in India's large diamond trading and craft market had come under cash flow "pressure" as a result of the measures introduced by Indian Prime Minister Narendra Modi's administration.
Petra has increased its capital investment in recent years, but chief executive Johan Dippenaar said this will now be reduced as the results, in terms of higher output, "come to fruition".
The company also said it had suffered a fatality in the last six months of the year at its Finsch mine in South Africa.
Dippenaar said: "Safety remains our highest priority at Petra and we are placing renewed focus on this vital area and relentlessly striving for a zero harm workplace."