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Use of Geologic Materials by Prehistoric Cultures

Red ball iconUse of Geologic Materials by Prehistoric Cultures

by E. Arthur Bettis III and William Green, State Archaeologist of Iowa


Modern society relies heavily on geologic materials for survival. Many of these materials are processed so that their natural form is no longer evident and their geologic origin not apparent. Prehistoric Native Americans also depended on geologic materials for survival. However, their use of various minerals, deposits, and landscape elements did not alter these materials to the extent that modern technology does. Ancient Iowans used geologic materials for everyday tools as well as in symbolic and ceremonial contexts. In many instances, these uses reflect a pervasive Indian view of unity with the environment.

Native Americans have lived in Iowa for more than 11,000 years. Until about 2,500 years ago, small bands lived by hunting game and gathering wild plants. These people, referred to as Archaic cultures, relied on stone, bone, shell, and wood for tools, and they made containers, rope, and clothing from vegetation and animal hide. Some Archaic groups built hide or mat-covered huts with floors dug into the earth.

About 2,500 years ago, Native Americans (Woodland cultures) began cultivating native plants in the rich soil along Iowa's streams to supplement their hunting and gathering. They also began to make pottery from local clays, and soon afterward they established trade networks for exotic items such as marine shell, obsidian (volcanic glass), copper, and mica. The following pages show some of these imports as well as local geologic materials used by Native Americans.


copper celt This rare copper celt from a southeastern Iowa site was probably used for ceremonial purposes by a person of high status (Woodland culture).


Projectile points Projectile points were made from chert (flint), a form of silica present in many Iowa rock units. Smaller points were used on arrows and larger points on spears, darts, or knives.


Mineral and rock material traded into Iowa between 100 B.C. and A.D. 300 includes mica from the Appalachians, hematite from the upper midwest, catlinite from southwest Minnesota, copper from the Lake Superior region, and obsidian from the Yellowstone National Park area.


Stone tools Stone tools were ground from igneous and metamorphic rocks collected from glacial deposits or stream gravels. Durable axes (top) and celts (bottom two) were attached to wooden or bone handles and used to break firewood, smash large bones, and girdle trees.
Preceding photos by Paul VanDorpe. Photo setups by Patricia Lohmann.


Pottery Pottery Pottery
Photos by Dave Benn.

Pottery clays were obtained from stream deposits or shale bedrock. Tempering materials such as sand, crushed rock, and burned clam shell strengthened the ceramic vessels. The surface of the large vessel (left) from northwest Iowa (ca. A.D. 400) has been roughened by twisted cords; the smaller vessel (middle) from northeast Iowa (ca. A.D. 600) has crescent-shaped designs on the body and (right) twisted-cord or fabric impressions on the rim.


platform pipe Ceremonial and religious objects were made from a variety of materials. This platform pipe, dating to ca. A.D. 100, is a bird effigy from southeast Iowa made from a northern Illinois claystone.


platform pipe This eastern Iowa platform pipe was carved from a crystal of calcite (ca. A.D. 100).


Petroglyph Images of humans, animals, and other forms were carved on sandstone cliffs and cave walls and on resistant outcrops of reddish Sioux Quartzite. A notable figure found on rock faces across northern Iowa is that of a thunderbird or a human portraying a hawk or eagle. Petroglyphs such as these probably had ceremonial importance (A.D. 1100-1200).


catlinite tablet Around A.D. 1400 to 1700, Indians in Iowa engraved elaborate depictions of bison (right), birds, and other creatures on flattened and polished catlinite tablets. Catlinite (also called "pipestone") is a soft claystone unit within the Sioux Quartzite Formation.


seeds corn cob Utilizing easily tilled soils in river valleys and in the Loess Hills, Iowa’s ancient farmers raised food crops, as shown by the tiny seeds of goosefoot (left) and a 2.5" corn cob (right). Both were recovered from 800-year-old storage pits.


 earth lodge Reconstructed earth lodge in Mills County.


excavated floor The excavated floor of this earth lodge shows an extended entrance, interior storage pits, a central fire pit, and the location of support poles and wall posts (A.D. 1000-1300).


fish weir At the fish weir near Amana, stream cobbles were arranged across the Iowa River channel. Fish could be speared or netted as they passed through the narrow downstream opening of the "V."


rockshelters Protective, overhanging ledges along valley walls (rockshelters) were frequently inhabited by Native Americans (Wildcat Den State Park, Muscatine County).
Preceding photos from Office of the State Archaeologist, The University of Iowa


burial mounds Woodland groups built burial mounds on high ridges or on terraces overlooking junctions of river valleys. Mounds may have also served to mark hunting territories, and as spiritual links with the Earth (Fish Farm Mounds State Preserve, Allamakee County).
Photo by Jean Cutler Prior.


For questions concerning artifacts or possible archaeological sites contact Office of the State Archaeologist, Iowa City.

Adapted from Iowa Geology 1993, No. 18, Iowa Department of Natural Resources