Binghamite (also called Silkstone and Cuyunite) is a type of agate stone found only on the Cuyuna iron range (near Crosby) in Crow Wing County, Minnesota Mining in the area uncovered deposits of the stone, but since mining operations were discontinued in the area many years ago the stone has become fairly rare. The stone has areas that are highly chatoyant similar to Pietersite or tiger's eye and when originally found was named American Tiger's Eye.