Sunstones
at Sunstone Knoll, Millard County Geologic information: Sunstone Knoll is formed of volcanic vents that erupted during the early Pleistocene (1.6 million years to about 750,000 years ago). These eruptions left deposits of basaltic lava and volcanic breccia (angular, broken rock fragments held together in a matrix of finer grained material). Sunstone is a transparent, yellowish