Binghamite, also known as silkstone and cuynite, is a type of agate the was found near iron ore deposits in the Cuyuna iron range near Crosby, Minnesota and is named after William Bingham who discovered it in 1936. Mining has been discontinued for a number of years so the stone has become increasingly rare and sought after by lapidary enthusiasts and collectors. Even the spoils, that were once available to collect are now depleted. Binghamite displays areas of chatoyant red, gold, and black similar to pietersite or tiger eye. When the pattern runs in level bands it is referred to as silkstone and when they run in all directions it is Binghamite.