AUSTRALIAN diamond mining group Ashton Mining Ltd says Australia’s Foreign Investment Review Board (FIRB) has extended its consideration of De Beers A$522m takeover offer. ”It is not unusual in large and more complex cases to take more time to consider them,” said Peter Biggs, acting general manager of the Foreign Investment Policy division in Treasury. De Beers offered A$1.62 for Ashton. However, that was topped by mining giant Rio Tinto Plc, which bid A$1.90 a share. Investors are punting on an even higher bid, with Ashton shares trading above the current offers. De Beers said late last month it was considering whether to increase its offer, which is aimed at grabbing Ashton’s 40.1% stake in Australia’s Argyle mine, the world’s largest diamond mine by production volume. – Reuters