The rocks of Never Summer Mountains are younger than most of the surrounding mountain ranges. They, along with the Rabbit Ears Range to the west, were formed by volcanic and intrusive processes 24–29 million years ago and consist mostly of igneous granitic formations along with preceding metamorphic formations. Most of the highest peaks in the range are granodiorite that was uplifted during the Miocene epoch. The range's highest summit, Mount Richthofen, is the remnant of an andesite volcanic plug. The Nokhu Crags in the north are mostly Pierre Shale dating from Cretaceous times. A large thrust fault underneath the Kawuneeche Valley thrust older Precambrian rocks on top of the younger Cretaceous rocks on the east side of the range. The southern peaks are Miocene-aged granite, and finally Precambrian-aged biotite gneiss and schist.