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 labradorite (a plagioclase feldspar mineral) found as crystals in these volcanic rocks and on the flats surrounding the knoll.

Directions:
From the west edge of the town of Delta (railroad overpass), travel west on U.S. Highway 6/50 about 4.3 miles to the State Highway 257 junction. Turn south on highway 257 and travel approximately 13.4 miles (just before mile-marker 56). A sign on the west side of the road marks the entrance to Sunstone Knoll on the east. Turn east onto the dirt road, cross the railroad tracks (watch for trains), and circle around the knoll to the east side. Please sign the register at the entrance. A private claim is on part of this site, but individuals are generously allowed to collect.