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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.
The Canadian quarry is no longer used, although there are quarries in Canada where prized black stone is gleaned. The Ojibwa use both the red and black stone for their sacred pipes. The red catlinite from the Pipestone quarries is the second softest rock in the world, and it lies under Sioux quartzite, the second hardest rock in the world. Only hand tools are used to reach the catlinite so it takes a long time to get to it. Only enrolled Native Americans are allowed to quarry for the stone at the Pipestone National Monument, and thus it is protected from over-mining. Another quarry is located near Hayward, Wisconsin on the reservation, which the Ojibwa have used for centuries. The stone there is harder than the stone from Pipestone National Monument.
Utah Pipestone has a more variable range of hard and soft forms, since it occurs as layers between deposits of harder slates. Utah Pipestone is a by-product of slate mining in Delta, Utah and several natural deposits in the area have been mined and used for pipemaking by Native Americans in the area for millennia. Minnesota Catlinite is buttery smooth, but contains quartzite like all forms of catlinite (which is what cements the rock particles together) and can be cut with a regular hacksaw or even a knife, it comes out of the ground a pinkish color often with a cream layer protecting it from the hard quartzite. It is weaker and more subject to breaking under stress than Utah pipestone
The term Catlinite came into use after the American painter George Catlin visited the quarries in Minnesota in 1835; but it was Philander Prescott who first wrote about the rock in 1832, noting that evidence indicated that American Indians had been using the quarries since at least as far back as 1637.
A large range of pipestones exist, not just those in Minnesota, and numerous native American tribes used a variety of materials and catlinites for pipemaking. Most Catlinite deposits exist beneath the level of groundwater or are in deep enough layers where the soil is constantly moist as the iron compounds which give catlinite its red color quickly convert into iron oxides when exposed to the elements and the stone degrades and breaks down.
In the United Kingdom, pipe-clay has meant a pale, whitish clay since the 18th century. The Oxford English Dictionary defines it as "fine white kind of clay, which forms a ductile paste with water". It is traditionally used for all sorts of polishing and whitening purposes as well as for making tobacco pipes and pottery.
Catlinite is often used to make the hollow tubes in pipeclay triangles.