Which type of rocks are most commonly found in mountains?

The three major types of rocks—igneous, sedimentary, and metamorphic—can all be found in mountains, but metamorphic rocks are the most common. These rocks form when existing rocks undergo transformation due to immense heat and pressure deep within the Earth’s crust. Over millions of years, this pressure changes the texture and mineral composition of the rock. For example, shale can turn into slate, and limestone can transform into marble. Mountain formation often exposes these rocks at the surface. In regions like the Himalayas or the Alps, granite (igneous) and gneiss (metamorphic) rocks are particularly abundant, revealing Earth’s dynamic geological history.