The naturally polished surface of an outcropping of schist creates an intriguing effect when reflecting sunlight. The rock formation -- actually nearly black -- is extremely rich in mica; and the mica crystals collectively reflect sunlight back to the viewer. Thousands upon thousands of people a year walk right by this outcrop, near the foot of Mt. Rushmore; but few notice. Instead, the faces of four U.S. presidents capture more photographic attention.
2 W Keystone SD (10 Jun 2) looking WSW