The high quality coal with low level of mineral contaminants means it can demand premium prices on world markets.

What has not changed is the industry's ability to produce good quality coal at an affordable price.

The last experiment was with spark-arresting equipment in response to lineside fires caused by poor quality coal.

It also enabled the incorporation of a wide firebox for burning poor quality coal.

The railway companies also experienced shortages of good quality coal.

When the mine reaches full capacity (expected in 2013), it will produce up to 12.2 million tonnes of high quality thermal coal.

The British needed a colony on the west coast of North America to provide good quality coal for their steamships.

The Minnie Pit was 359 yards deep and had access to five seams of thick, good quality coal.

More important was the coal mining, which provided high quality coal, principally used in forges.

One of Hawksworth's modifications in changing the design was to equip it better to cope with the low quality coal available during the war.