Petra Diamonds took a knock on Tuesday after it became aware that 43m shares held by Awal Bank have been placed by its administrators, RBS Capital Markets, with both UK and international institutions at a price of 190p per share.The other 13.2m shares held by Awal Bank are subject to a 90-day lock-up. The group on Monday posted annual production figures above expectations at 3.1m carats, helping revenue jump 17% to $42.6m. Shares had fallen 11.18% to 192.39p by 11:49.NR