Catlinite

Catlinite (also called pipestone or pipeclay) is a type of argillite (metamorphosed mudstone), usually brownish-red in color, which occurs in a matrix of Sioux quartzite. Because it is fine-grained and easily worked, it is prized by Native Americans for use in making sacred pipes such as calumets (Fr: "hollow reed") and chanunpas. Pipestone quarries are located and preserved in Pipestone National Monument outside of Pipestone, Minnesota, in Pipestone County, Minnesota, and at the Pipestone River in Ontario, Canada.