During the Ice Age, great glaciers tore at the earth, spreading Lake Superior agates across much of Minnesota. The best places to find Lake Superior agates are gravel pits in certain areas that were in the path of glaciers coming out of the Lake Superior basin. Nebraska celebrated its Centennial in a really down to earth way. Both are agates. Nebraska agates are found in the Ogallala National Grasslands north of Crawford, in northwestern Nebraska.
Blue chalcedony is a pale stone, sometimes dark internally with bands of blue and white.
Blue agates are used extensively in jewelry. Prairie agates appear as alternating layers of variously colored chert of granulated crytocrystalline quartz. They lack the bands of that characterize most agates. Prairie agates have a rounded irregular shape and are popularly used to make jewelry. First discovered near Fairburn, South Dakota, this agate is found primarily in an area extending from Orella, Nebraska, to Farmingdale, South Dakota.