Blue Chalcedony (Blue Agate)
Nebraska designated blue chalcendony (commonly called blue agate) as the official state gemstone in 1967. Blue chalcedony is a pale stone which sometimes has a dark internal form with bands of blue and white and often has a colorless streak. Blue agate is often used to make jewelry.
Blue agate is found in northwestern Nebraska, where it formed in wind-blown silt and claystone deposited in the Chadron Formation of the Oligocene Age.