Agate Fossil Beds National Monument is a small park in the northwest corner of Nebraska, with only 2,700 acres of federally managed land included in the 3050 acres within the park boundary. The park takes its name from thin lenses of agate (White River Silicate Group) in the area, which range in color from amber to light gray. Miocene-age rocks are exposed in the park in the bluffs above the Niobrara River wetlands and contain an excellent fossil record. Much of the geologic history is recorded in the natural features found at the park today.