Catlinite (also called pipestone) 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, primarily those of the Plains nations for use in making ceremonial pipes such as chanunpas. Pipestone quarries are located and preserved in Pipestone National Monument outside Pipestone, Minnesota, in Pipestone County, Minnesota, and at the Pipestone River in Ontario, Canada.