Parys Mountain is a bit of a geological misfit. The mineralised zones are the result of molten lava flowing onto the seabed millions of year ago when Wales was part of the ocean floor. These volcanic intrusions carried on for hundreds of thousands of years and gradually built up multiple layers of volcanic massive sulphide, which created a complex yet rich ore body. Volcanic massive sulphide ore deposits are often of interest as sources of ore containing copper, lead and zinc.