. "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 sacred pipes such as calumets (Fr: \"hollow reed\") and chanunpas."@en . .