The summit is very similar to that of Pen y Fan: flat and anvil-shaped. It is similarly formed from the relatively erosion-resistant Devonian age sandstones from the Upper Old Red Sandstone known as the Plateau Beds. The rock strata are clearly visible at the edge of the escarpment, where they form a resistant edge to the cliff. The same strata are visible all along the escarpment facing north, as well as the rearward edge facing south-east and lying behind the main peaks. The same Plateau Beds recur in the Black Mountain (range) to the west, and cap the summits of Picws Du and Fan Foel, as well as forming steep cliffs below the peaks.