Ground Stone Artifacts

Series in Ancient Technologies 

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Mano and Metate

A wide range of prehistoric artifacts were formed by pecking, grinding, or polishing one stone with another. Ground stone tools are usually made of basalt, rhyolite, granite, or other macrocrystallineigneous or metamorphic rocks, whose coarse structure makes them ideal for grinding other materials, including plants and other stones. Native Americans used cobbles found along streams and in exposures of glacial till or outwash to produce a variety ground stone artifacts. The process by which ground stone tools are manufactured is a laborintensive, time-consuming method of repeated pecking and grinding with a harder stone, followed by polishing with sand, using water as a lubricant. 

The form of a stone axe was created by pecking with a hard hammerstone
The form of a stone axe was created by pecking with a hard hammerstone

In North America, axes, celts, gouges, mauls, plummets, and bannerstones began to appear early in the Archaic period, made from hard igneous or metamorphic rocks. Cobbles with small shallow cupped depressions, called anvil stones or nutting stones, also came into use during the Archaic period. Discarded ground stone tools sometimes later became convenient raw material for use in stone boiling, lining roasting pits, or ringing hearths, thus ending their useful life as fire cracked rocks. 

Three-quarter grooved axe
Three-quarter grooved axe

To facilitate hafting, axes were grooved, either completely around the four faces of the tool, or on three of the four faces. These groove patterns thus give rise to the terms “full” and “threequarter” grooved axes. 

Celt
Celt 

Rarely, grooves were placed only on the two flattened faces of an axe; in the Midwest such tools are known as Keokuk axes. Celts are similar to axes but lack the groove and were hafted with the bit perpendicular to the axis of the handle, rather than paralleling it, as with an axe. Axes, celtsgouges, and mauls are generally considered to be woodworking tools and are often found in areas that were once forested or still retain the native tree cover. 

Finished axe hafted to a wood handle
Finished axe hafted to a wood handle 

During the Late Archaic, Woodland, and Late Prehistoric periods ground stone technology began to be applied to softer sedimentary and metamorphic rocks for making other kinds of artifacts. For example, limestone was used for making pipes, hematite for celts, sandstone for arrow shaft abraders, and small bowls were shaped from steatite. 

Middle Woodland limestone platform pipe
Middle Woodland limestone platform pipe 

Catlinite is a relatively soft, reddish metamorphic rock found in southwestern Minnesota that is wellknown for use in calumet and disc-bowl pipes by Plains tribes. With the development of horticulture came the need for tools to process grain, and large flat blocks of quartzite or granite were pecked and ground into dishshaped grinding stones called metates to grind corn or other seeds into meal. 

Catlinite elbow and disc-bowl pipes
Catlinite elbow and disc-bowl pipes 

Some ground stone tools were created incidentally by abrasion with other tools. Manos, for example, are handheld stones used in conjunction with metates or grinding slabs, and develop their ground surfaces through wear. Cobbles used as hammerstones in flintknapping and ground stone pecking retain the scars developed from use, often appearing as pitted and flattened areas along their perimeters. 

Matched pair of sandstone arrow shaft abraders
Matched pair of sandstone arrow shaft abraders 

Ground stone technology also was used to produce artifacts of personal adornment. Gorgets, beads, and ear spools enhanced the appearance of the bearer and perhaps functioned as status symbols. Such artifacts were drilled to permit suspension from a cord by spinning a narrow pointed stone, hardened stick, or bone between the hands against the stone, using sand as an abrasive. The hole was drilled part way through on one side of the object and the remainder of the hole was drilled from the opposite side.

Gorgets with holes drilled for suspension
Gorgets with holes drilled for suspension 

The drilling process results in a biconical hole that is narrowest near the middle of the object. Larger-diameter holes could be drilled using a hollow bone or reed along with sand and water. A by-product of the hollow drill was a narrow cylindrical core of the parent rock. Such cores of drilled ground stone artifacts have been found on archaeological sites. 

A few very special artifacts were used in the ritual or ceremonial realms of certain prehistoric groups. At village sites of northwestern Iowa’s Late Prehistoric Mill Creek culture, small lens-shaped quartz or basalt discoidals and thunderbird effigies of limestone and catlinite have been found. The discoidals resemble old style ceramic or brass doorknobs in size and shape and are sometimes simply referred to as “doorknobs” by artifact collectors. Larger, biconcave stone discs four to five inches in diameter called chunkey stones were used by Mississippian societies of the southeastern part of the continent in a game of the same name. 

Late Prehistoric age "doorknob" discoidal and chunky stones
Late Prehistoric age "doorknob" discoidal and chunky stones 

Similar items have been found on Late Prehistoric Oneota villages in northwestern Iowa. Along with grinding and drill for pipes, catlinite also lends itself well to fine line engraving with a sharp tool, and a few small catlinite tablets engraved with complex symbols and pictographs have turned up on northwestern Iowa Oneota sites. 

Catlinite tablet with engraved pictograph of a buffalo
Catlinite tablet with engraved​ pictograph of a buffalo