RAPAPORT... Petra Diamonds' shares fell more than 15% in early trading Monday after theminer reported a significant slide in rough-diamond prices at its flagshipCullinan asset. The average price plunged 31% to $96 per carat at the miner'sSouth African asset in the first fiscal half ending December 31. That compares with an average of $140 per carat for the nine and a half years spanning July 2009 to December 2018, the miner said Monday. The company's net debt increased to $557.2 million as of December 31 compared to $538.9 million atSeptember 30. Even so, sales for the first fiscal half climbed 8% to $207.1 million from three tenders, while sales volume jumped 15% to 1.7 million carats.Production rose 10% to 2 million carats as Petra continued to ramp up output ata new portion of Cullinan. Petra maintained its production forecast of 3.8 million to 4million carats for the full fiscal year ending June 30, compared to the 4.6 millioncarats it recovered in fiscal 2018. Image: Inspection at Cullinan prior to production. (Petra Diamonds)