RAPAPORT... Petra Diamonds' revenue jumped in the first fiscal quarter as the miner sold several high-value stones, with the category contributing nearly half of total sales.Revenue surged 48% to $114.9 million for the three months ending September 30, the company reported Tuesday. Petra offered three exceptional diamonds during the period, including a 39.34-carat blue, which sold for $40.2 million, a high-quality, 342.92-carat white, which went for $10 million, and an 18.30-carat blue that brought in $3.5 million. The shift to a higher average value outweighed a 36% drop in sales volume to 578,186 carats. Sales were also boosted by continued strong market demand, which has lifted prices, Petra CEO Richard Duffy noted. Prices rose 3% on a like-for-like basis compared with the fourth fiscal quarter. Production fell 12% year on year to 861,991 carats for the quarter, mainly due to a reduction in output at the Finsch mine in South Africa, where the company shifted to a lower-grade section and saw a planned decline in processing volumes.The company is also experiencing technical challenges with the C-Cut block of its Cullinan mine. Total production from the deposit will likely be toward the bottom half of its original guidance of 1.7 million to 1.9 million carats, it said. The company is still on track to recover a total of 3.1 million to 3.4 million carats for the full year as it ramps up at the Williamson mine in Tanzania, which had previously been on care and maintenance. Petra expects total output from that site to add between 220,000 and 270,000 carats for the year.Image: The Cullinan mine. (Petra Diamonds)