Mt Gibson chief executive Jim Beyer will never be happy that a wall collapse caused a four-year outage at his company's flagship mine, but the changing nature of Chinese iron ore demand over that period has softened the blow.

The high-grade iron ore that comes out of Mt Gibson's Koolan Island mine was fetching a premium of 3 per cent to 5 per cent above the benchmark iron ore price in the weeks prior to the November 2014 collapse of a seawall that separated the mine from the azure waters of the Timor Sea.