The Rathdowney Trend, stretches 40 kilometres, between the towns of Abbeyleix and Thurles. The region is a broad plain drained by the Rossetown and Drish Rivers, tributaries of the River Suir, which flows into the sea at Waterford. Exploration of the Rathdowney Trend during the late 1960s and early 1970s identified sporadic occurrences of lead and zinc, although the first significant mineralisation was not discovered until 1984. Lisheen Mine is also in the Rathdowney Trend.
Galmoy is exclusively an underground operation. Initially the mine used room-and-pillar methods exclusively but subsequent modifications introduced both benching and drift-and-fill systems where conditions are appropriate, as a means of maximising ore recoveries. At the same time the mining method is designed to ensure that no waste rock needs to be hauled to the surface.
In 2008 Workers at Galmoy Mines were told the mine is to close completely on a phased basis by July 2011. Management said dwindling zinc resources at Galmoy and a drop in the price for metal worldwide were reasons to close the plant.
Production from the mine ceased in May 2009. However some ore remains unmined and plans are being formulated to consider means of recovery of some or all of this ore.
The Galmoy ore bodies are breccia-hosted, generally stratabound lenses of predominantly massive sulphides consisting of sphalerite, argentiferous galena and pyrite / marcasite in variable combinations. Hosted in Lower Carboniferous rocks, they occur at the junction of an argillaceous bioclastic limestone (below) and the dolomitised Waulsortian limestone above.