Sales at Petra Diamonds sparkled in the first half of the year as it was boosted by a recovery in the market for precious gems. Revenue rose 48% to 228.5 million US dollars, while net profit came in at 35.2 million US dollars. However, Petra added that it is "mindful" of the potential for full-year production to come in at the lower range of expectations due to labour rows linked to the construction of a new diamond mine in South Africa.