Where to Find Chalcedony in Nebraska

Nebraska chalcedony shows up in the Pine Ridge country of the northwest and along the Niobrara River drainage. Box Butte and Sioux counties produce "prairie agate," a banded chalcedony with brown and red fortification patterns, eroded from Tertiary lake-bed silica. The Agate Fossil Beds National Monument area is itself closed to collecting, but the surrounding ranch country and Sioux County gravels still yield small chalcedony nodules. The North Platte River gravels in Cheyenne County add tide-tumbled chalcedony float carried from older volcanic sources to the west. Most Nebraska chalcedony is small and concentrates after seasonal rains expose fresh gravel.