Despite the fall in sales to 403,000 tonnes during the quarter, Gloucester was able to change its coal mix to favour the higher priced coking coal, increasing production by 37%.

"Changes in the mix of coal from each of the Company's pits reflects the optimisation of operations through the blending of coal, and a focus on the production of the higher value coking coal during times of port capacity constraints," the company said.

Gloucester pointed out coal from the Roseville operation was particularly improving the quality of its mix.

The company said it was on track to increase output to 2.8 million tonnes in 2009-10.