Geology

Quarrying Process

The actual quarrying of pipestone is often an unappreciated part of the tradition surrounding pipemaking. The task of extracting pipestone from the earth is a slow and labor intensive process and the hand tools used today are not much more advanced than the tools and methods used in centuries past. The process can require many days of physical labor with only the use of hand tools such as sledgehammers, pry bars, chisels, wedges, and steel bars allowed. For someone not already in good physical condition the process is slowed or should not be attempted at all. Visiting with someone with quarrying experience prior to applying for a quarry permit is extremely helpful.

Depending upon the specific quarry, experience has shown that quarrying time can be estimated at two to six weeks. The layer of pipestone is sandwiched between layers of very hard Sioux Quartzite rock. Depending upon a quarry's location on the quarry line the upper layer of quartzite can be four to ten feet thick above the pipestone layer. Prairie plants and soil varying in depth from one to six feet cover the upper layer of quartzite.

By use of shovels and wheel barrows the soil layer is dug up and moved to the rubble piles at the rear of the quarries. All subsequent quartzite pieces are also moved to the rubble pile. Do not place soil and quartzite pieces in front of the quarry as you will eventually end up moving them again to continue quarrying.

The upper layer of quartzite is itself composed of multiple layers of quartzite, with vertical fractures and cracks in the rock. Wedges or chisels are placed into these cracks and then driven down with sledge hammers to break loose individual blocks of quartzite. Upon loosening a piece it is worked free with a steel pry bar and allowed to drop to the floor of the quarry. Heavy sledge hammers are then used to break the bigger chunks of quartzite into smaller manageable pieces that can be lifted and thrown out the back of the quarry. The process of breaking out the quartzite is repeated many times until the pipestone layer is exposed.

The smaller pieces are also used in building a rock retaining wall along the front of the rubble pile. The rock wall serves as a "fence" of rock so that as additional quartzite and soil are thrown or stacked at the rear of the quarry the fence will prevent the rubble pile from collapsing back into the quarry. Building a retaining wall is an essential part of managing your quarry and a very important safe-guard for quarriers.

Once the pipestone is exposed, care must be taken in removing the stone as it is very fragile and when handling large slabs it can break. The pipestone layer may vary from 10 to 18 inches thick and it too is composed of multiple layers from 1 ½ to 3 inches thick. Individual layers are carefully removed one slab at a time by driving wedges into the natural horizontal seams. The natural vertical cracks in the quartzite carry down through the pipestone which allows the quarrier to remove the pipestone layers in irregularly shaped slabs.

Geologically the quarries are located in the bottom of a bowl shaped drainage. In the spring and early summer months groundwater from rain and snow melt collects in this low laying area, filling the quarries with water. Most quarriers prefer to work during the summer to late fall months to avoid the groundwater problems. Monument staff will assist quarriers by pumping water out of the quarries, but only upon 2 days advance notice of when quarrying is planned. Often, when it is high, groundwater will flow back into the quarries as fast as it is pumped out. Since continued pumping will not reduce the water level it will not be attempted during these high groundwater periods. To avoid wasting a trip, please call head to find out the groundwater levels before planning any quarrying.

Weather conditions during the summer months, consists of high temperatures and high humidity. Plan accordingly to reduce the chances of dehydration and heat exhaustion. Drink plenty of water and take frequent rest breaks. Moderate sized erectable shades are allowed along with folding chairs and some additional comfort items like coolers. No camping at the quarries is allowed. Mosquitoes, poison ivy, ticks, and unstable footing in the quarries are all hazards encountered. While there is a monument wide regulation restricting foot travel to paved paths, quarriers are allowed to walk in the prairie as they work around their quarries. To preserve the prairie plants please avoid any unnecessary foot travel across the prairie.

The solid bedrock of the Pipestone National Monument is the Sioux Quartzite, a thick stack of ancient layered rocks exposed today in parts of Southwest Minnesota, southeastern South Dakota, and northwest Iowa. 

The Sioux Quartzite consists of three rock types that were originally layers of mud (pipestone), sand (quartzite), and gravel (conglomerate) which, according to scientists, were deposited at some time between 1,750 and 1,630 million years ago. 

The unique variety of pipestone at Pipestone National Monument is called catlinite. It consists largely of microscopic crystals of pyrophyllite (pie-raw-fill-ite), diaspore (die-ah-spore), muscovite (musk-oh-vite), and kaolinite (kay-oh-lihn-ite). Traces of the iron bearing mineral hematite (heem-ah-tite) give the catlinite its red color. Most other red pipestones found in the world contain the mineral quartz; catlinite has little or none. 

Catlinite formed when mud layers were buried within the earth, under temperature and pressure conditions very different from those at the surface. The original minerals were unstable in this new environment, and their chemical components recombined to form new minerals. 

The catlininte beds are sandwiched between thicker beds of quartzite. Most of the sand grains of which the quartzite is made are rounded crystals of quartz "glued" together by other quartz crystals that grew between the sand grains after the layers were buried. After millions of years of heat and pressure pressing the grains together, the rock is presently a mineral harder than ordinary steel. 

Although Sioux Quartzite is extremely hard, the underlying layers of catlinite are very soft. Since the catlinite contains no quartz, subjection to the same natural heat and pressure metamorphosed it into a very dense material which is roughly the same hardess as a human fingernail. It can therefore be easily carved using only the simplest of tools.       

At least five different catlinite layers are now exposed in the quarries at the Monument. These extend in a roughly north-south line which is two-thirds of a mile long, following a zone with the Sioux Quartzite containing many pipestone beds.

Quarrying

Located in rural southwestern Minnesota, the pipestone quarries are considered a sacred site by many American Indians. For the last 2000-3000 years tribes across the central region of North America have traveled to this site to quarry. Today, they still travel long distances to continue the tradition of pipemaking.

"An Act to establish the Pipestone National Monument in the State of Minnesota, approved August 25, 1937, (16 U.S.C. sec. 445c) Sec. 3. The quarrying of the red pipestone in the lands described in section 1 is hereby expressly reserved to Indians of all tribes, under regulations to be prescribed by the Secretary of the Interior."

With passage of this law Congress provided direction to the National Park Service to allow for the continued quarrying of pipestone. Legal opinions have since concluded that Congress's intent was that Sec. 3 applied to American Indians enrolled in tribes recognized by the U.S. Government. While this conclusion may exclude some Indians from tribes not yet federally recognized it does include members from over 562 tribal groups. The monument utilizes the Federal Register notice of November 25, 2005 (Vol. 70, No. 226) in determining the status of an applicant.