Petra Diamonds said first-quarter production fell 4%, contributing to a 17% slide in revenue.
Diamond output fell to 1,053,817 carats, down from 1,097,523 carats in the same period last year, mainly due to a planned reduction in tailings production at Finsch and the Kimberley Ekapa mining joint venture.
Revenue fell 17% to US$78.7m, from $94.7m. No sales from Williamson in Tanzania were included, due to a parcel of diamonds from the mine being detained by the Tanzanian government.
The company maintained its full year production guidance of around 4.8 to 5.0 Mcts.