MINING firm Petra Diamonds has reported its highest quarterly production since the company launched in 1997, at 833,744 carats for the first quarter of 2014-15, up two per cent from the 816,735 carats recorded at the same time last year. Revenue also grew to $100.8m (£62.5m), up 55 per cent on $65.1m in 2013-14, despite total sales falling by 10 per cent to 532,250 carats. Shares fell 2.9 per cent yesterday, closing at 170.1p. The company said the diamond market is currently exhibiting its “customary post summer softness”, which is typically the quietest time for rough diamond sales. However, it expects the market to firm up once the festive sales period starts near the end of November. Petra announced the sale of a 232 carat white diamond for $15.2m last week. The company also runs the Williamson mine, which produced the Williamson Pink. That stone was given to the then Princess Elizabeth as a birthday present in 1947.