Mullach nan Coirean stands in stark contrast to the adjoining Stob Bàn, which is a pointed and light coloured peak, owing to its crown of quartzite. Mullach nan Coirean differs, being a large sprawling mountain of ridges and corries with its granite rock giving the mountain a definite red shade (see picture). The mountain has three north facing corries: the finest of these is Coire Dearg (Red Corrie) which is drained by the Allt a' Choire Dheirg into Glen Nevis and is overlooked by Mullach nan Coirean's South East Top (917 metres) which is listed as a top in Munro's Tables. The South East Top was previously called Coire Dearg Top but was changed to avoid confusion as the main summit also overlooks Coire Dearg. The other two northern corries are smaller: Coire Riabhach also drains to Glen Nevis while Coire a' Mhuillinn empties further west into the River Kiachnish which delineates the mountain's western boundary. A fourth corrie, Coire Carach stands on the mountain's southern slopes.