Barnes Butte is a rhyolite dome of volcanic rock in Crook County, Oregon, United States located partly within the city of Prineville. Barnes Butte is composed of welded tuff and is a part of the Crooked River caldera. It was the site of a 1940s mercury mine. In 2015, a BLM cleanup of mercury was done to reduce the health risk to residents of nearby IronHorse neighborhood and the Barnes Butte Elementary School.