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The Process & Mines

Coal is a "fossil fuel" formed by the decomposition of land plants' that have accumulated in swampy or low-lying areas.

Land plants first appeared over 400 million years ago during the Silurian Period. Although it was not until the Carboniferous Period of 300 million years ago, when plants developed sufficiently to produce major forests, that the continual build-up of decaying plants had begun the first step towards becoming coal.

In swampy areas the plant and tree debris gathered, as each new layer of dead and dying plants increased in thickness, these vast swamps slowly sank. "Humification" or the rapid decaying of the plant material results in the formation of "peat". The peat becomes covered with new sediment layers, the lack of air reaching the peat starts the second step of the "coalification" process, the combined effects of time, temperature and pressure convert the peat into brown coal, then sub-bituminous coal, bituminous coal and finally anthracite. The last three coals in the process are usually called black coal.

The different layers of sand and mud produced seams of clay between the coal seams. These seams are clearly seen in the different "batters" (flat areas in the mine from which coal is removed) as varying shades of brown.

These old sand and mud deposits are significant to mining operations as these sands are below the open cuts and contain water at very high pressure. This water must be pumped from under the mine in a controlled manner. If it were not pumped out, the water would have enough power to lift the open cut floor, causing flooding and dangerously unstable batters. Geologists call this water bearing sands, "aquifers".

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