Mitsubishi Corporation has begun production at the Clermont thermal coal mine in Australia.
The first coal has been delivered to neighbouring Blair Athol mine, from where it will be transported to a port for export.
The Clermont mine, constructed in 2007 and one of Australia's biggest thermal coal mines will reach its full capacity of 12.2 million tons of thermal coal each year by 2013.
The first exports from the mine, to begin in early May, will be sold mainly to Japanese companies.
The mine holds 189 million tons of marketable reserves, with a mine life of 17 years.
The mine is 50.1% owned by Rio Tinto, 31.4% by Mitsubishi, 15% by Japan's Electric Power Development and 3.5% by Japan Coal Development.