At an ancient time the Great Spirit, in the form of a large bird, stood upon the wall of rock and called all the tribes around him, and breaking out a piece of the red stone formed it into a pipe and smoked it, the smoke rolling over the whole multitude. He then told his red children that this red stone was their flesh, that they were made from it, that they must all smoke to him through it, that they must use it for nothing but pipes: and as it belonged alike to all tribes, the ground was sacred, and no weapons must be used or brought upon it.

-- Sioux account of the origin of the pipestone, as recorded by George Catlin, 1836.

Pipestone (Catlinite) is the sacred red clay stone that American Indians use for making prayer and ceremonial pipes. It has also been used for generations in Zuni for carving fetishes. It is found in only a few places in the world. The best quality pipestone comes from southwestern Minnesota. It ranges in color from pale pink to brick or blood red and normally has small lighter spots - referred to as "stars" - scattered throughout. Pipestone is smooth to the touch, can be easily carved and takes a high polish.

Modern science tells us that catlinite is a metamorphic claystone argilite. Metamorphic rocks are those that started out as one thing but were changed in structure or composition into something else through the processes of heat, pressure or both. Claystones are sedimentary rocks that include varying quantities of clay minerals. Argillites are claystones or shales that have undergone higher degrees of hardening than shale but which lack the distinctive lamination and cleavage of slates.

Mineralogically, catlinite is made up of diaspore, pyrophyllite, muscovite and hematite oxide, along with traces of anatase and chlorite. The hematite (iron ore) oxide is what gives the stone its rich red coloring. Chemically, cat linite breaks down into the following constituents: silica (49.01 percent), alumina (35.17 percent), magnesia (0.23 percent), water (5.87 percent), potash (5.62 percent), ferric acid (3.06 percent), titanium dioxide (0.44 percent), ignition–less total water (0.24 percent), lithium oxide (0.16 percent), soda (0.06 percent) and calcium oxide (0.05 percent).² In addition, significant amounts of calcium, potassium, rubidium, strontium and yttrium in the best catlinite samples indicate metasomatism. This is a metamorphic process in which chemical changes occur due to reactions with external materials. The Occupational Safety and Health Administration catalogs catlinite under code number 1499 as a nonmetallic, nonfuel mineral.³

Catlinite is found beneath beds of the much harder rock Sioux quartzite, in layers that are typically two inches to six inches thick. Veins of catlinite were formed between 1.6 billion and 1.8 billion years ago. River deposits of sedimentary clays, also called “mud puddle deposits,” gradually built up, and the weight of overlying Cambrian-era Sioux quartzite compressed the quartz-poor clays into what is now catlinite. Because catlinite itself contains little or no quartz, it is softer than the quartzite overburden and thus lends itself to carving with harder stone or metal tools. It registers 2.5 on Mohn’s Geological Scale of Hardness, putting it at about the same hardness as a human fingernail, and is a bit like soapstone in workability.