Gleision Coal Mine was situated above the banks of the River Tawe, near the town of Cilybebyll. It operated as a drift mine from the early 1960s, producing up to 200 tonnes of coal a week.
Tragically on 15 September 2011 during routine blasting, water flooded the mine, resulting in the deaths of four miners. The mine manager and mining company were subsequently charged but found not guilty of negligence.