Stone Mountain is a pluton, a type of igneous intrusion. Primarily composed of quartz monzonite, the dome of Stone Mountain was formed during the formation of the Blue Ridge Mountains around 300 -- 350 million years ago (during the Carboniferous period), part of the Appalachian Mountains. It formed as a result of the upwelling of magma from within the Earth's crust. This magma solidified to form granite within the crust five to ten miles below the surface.

Answer this question based on the passage: what type of geologic feature is stone mountain? Let's have some stream of consciousness first.
To answer the above question, the relevant sentence is: Stone Mountain is a pluton, a type of igneous intrusion. So, the answer is a pluton , a type of igneous intrusion.