Molybdenite is also visible in outcrops on this exposed laccolith. There is likely to be a giant laccolith of syenite below Cygnet. The dome is referred to as a doleritic laccolith. His doctoral thesis was a petrologic study of the Boxelder laccolith. The rock is a thick gabbroic-dolerite laccolith, which is a source of roadstone. Geologically, the mountain is a laccolith, a type of igneous intrusion. Mount Lamborn is an eroded igneous intrusion that geologists call a laccolith. His work on the laccolith influenced Grove Karl Gilbert's own work on the same. Significant amounts of syenite and shonkinite can be found in the laccolith. The laccolith ranges are much younger and have a very different geologic origin. Shortly after the laccolith intrusions in the north, volcanic activity began to the south. A laccolith is an igneous intrusion injected between two layers of sedimentary rock. The laccolith was formed during a 20 million-year period of volcanic activity. As the surrounding, softer material has weathered away, the laccolith has become increasingly exposed.