* Apr-Oct exports down 25 percent y/y
* Goa exporters say fear mining ban (Adds quote, details)
NEW DELHI, Nov 21 (Reuters) - Iron ore exports from India, usually the world's third biggest supplier of the ingredient for steel, could fall a third to 65-70 million tonnes in the year to March 2012, the head of a major exporter, Sesa Goa, said on Monday.
India's iron ore exports were already down 25 percent in April to October, hit by stalled shipments because of a legal wrangle in Karnataka, which normally accounts for a quarter of exports, and the pinch of high transport costs.
The western state of Goa, which was the top exporter last year, could ship 45-50 million tonnes, down from 54.42 million tonnes in the year earlier period, Sesa Goa Managing Director P.K. Mukherjee said at an iron ore industry event.
Goa shipped 19.76 million tonnes in the April to October period, down 6.15 percent.
Most of India's iron ore exports go to China, which has the world's largest steel industry. The country used to export about half its annual production until Karnataka introduced a ban on shipments in July 2010.
That ban was overturned by the Supreme Court in April this year but exports from Karnataka have yet to resume as state authorities take time to put tracking equipment and other safeguards against illegal mining in place.
The Supreme Court has now banned mining in three areas of Karnataka on environmental reasons.
Mukherjee said any mining ban in Goa would hit exports from that state too.
"If you see Goa's contribution, then you can work out what impact a ban can have on exports," Mukherjee said.
India, which wants to conserve iron ore for its domestic steel industry, hiked export duty in its last budget in February while freight rates were hiked 50 percent in January.
Iron ore prices slumped 31 percent in October but have recouped most of that in the last couple of weeks, and a sharply weaker rupee against the dollar could also help India's exports.
And although China's demand for steel is still sluggish, the world's biggest iron ore consumer has piled up record stocks ahead of the winter there.
Sesa Goa's shares ended down nearly 7 percent to 171.25 rupees on a slightly weaker stock market on Monday, on expectations iron ore spot prices might fall again this week after their recent rally. (Writing by Jo Winterbottom; Editing by Subhadip Sircar)