The local share market had a positive end to the week, boosted by a healthy gain for the mining sector. The All Ordinaries index rose 17 points or 0.3 per cent to close at 5,560, while the ASX-200 gained 18 points to 5,567. Much of the gain was driven by a 2.3 per cent rally by BHP Billiton. The miner announced early this afternoon that the board has identified a demerger of non-key operations as its preferred option to focus on iron ore, copper, coal and petroleum. Rio Tinto rose by a more modest 0.4 per cent but gold miner Newcrest fell 0.7 per cent. It was a mixed session for finance stocks. Westpac gained 0.4 per cent, NAB 0.25 per cent and the Commonwealth 0.2 per cent. ANZ fell 1.1 per cent despite reporting a record rise in third-quarter earnings.