The Precambrian gneiss rocks of the Owl Mountains constitute the oldest part of the Sudetes and are among the oldest in Europe. Other deposits include migmatite rocks, to a lesser extent also amphibolite, serpentinite, granulite, and pegmatite. Except for the summit clearings and the mountain passes, the Owl Mountains represent the spruce-clad type of mountains. There may be also observed a rare natural occurrence of beeches and European yew.