Cupstones of Adair County, MO
Adam Brooke Davis
Truman State University

Draft of 7-17-02

Variously known as "cupstones," "anvil stones," "pitted cobbles" and "nutting stones," among other names, these roughly discoidal or amorphous groundstone artifacts are among the most common lithic remains of Native American culture, especially in the Midwest, in Early Archaic contexts. They have received little study, perhaps because edged tools and weapons have more intrinsic interest to collectors, but closer study of them might reveal something of domestic practices and toolmaking technology.

The use of these items is unknown -- although the ad hoc terminology implies function(s). Professor Betsy Delmonico of Truman State University has pointed out that very similar artifacts are known from the Indian subcontinent, often incorporated into clearly decorative and cultic objects, and the phenomenon has been observed in Celtic Europe and even in Australia and Israel. Some insist the items are "false" artifacts, that is, their form results from natural processes rather than human activity. However, no one has yet described processes that might both produce such effects and also explain the distribution of the effects and the objects. Certainly air-bubbles in stone, broken open and eroded, could produce some of these phenomena. The objects are familiar in Illinois, Ohio, Indiana, Arkansas, Kentucky, Tennessee, the Carolinas, Alabama and Mississippi, and occur elsewhere as well. Often they have been collected as oddities, and are found in residential rock-gardens. All of the stones pictured here were recovered from Adair County MO by Adam Brooke Davis, from private land, with permission, and none were in association with burials or sites of archaeological value.

When not carried by natural forces into creekbeds, these objects are frequently surface-found on ridge-lines and at apparently random sites in the woods, frequently near streams and rock-shelters, suggesting a possible link to hunting, or with the combined activities of a seasonal hunting/gathering camp. Excavated specimens are associated with food-processing, including potsherds and food-remains. The author has found several near the remains of small and single-use fires, but the number of sites is insufficient to make a compelling case for the association. If used for mast-processing, one would expect the objects to be associated with relatively long-term occupation-sites. A camp-midden on the Chattahoochee River ( yielded twelve specimens, along with grinding slabs and the hulls of acorns and hickory nuts, which were known in historic times to be prepared either as gruel or used to thicken soups. The pits may be adaptations for additional uses to implements primarily classifiable as other types, for example manos and metates. Interestingly, the only test using contemporary immunological analysis, carried out on a specimen from California, gave a positive result for trout residue alone ( Specimens found near Arkansas petroglyphs lead George Sabo III and Deborah Rowland Sabo of the Arkansas Archeological Survey to suggest the impressions were used to grind pigments for coloring rock art (

Two uses not yet discussed include making fire by the bow and drill method, in which case a stone might have been used to anchor the upper end of the shaft, while a string, held taut with a bow and wrapped around the shaft, would provide rotary motion to create friction on a slab of wood on top of which tinder had been piled. Amateurish experiments have failed to demonstrate the principle, but the author makes no claim to fire-making skill under any circumstances. A few specimens show fire-marking, which may indicate that they served as the base-socket for the fire-drill, with tinder piled around the rotating shaft -- or they may have found their way simply and accidentally into a fire. A much more comprehensive study, carefully correlating the closely observed features of these objects, is necessary.

Another possibility might be that the impressions provided a socket to hold the butt end of a shaft steady during peeling and straightening. The author has tested this hypothesis with a shaft-straightener or abrader found near one of the cupstones--

and the method is at least practical. Larger indentations might have been used to steady spear-shafts. Multiple impressions might suggest communal, industrial manufacture of implements and weapons. Stones with multiple impressions of similar size, yet which would not be simultaneously accessible are difficult to explain. Most of the objects are of a size to be held in the hand, some as small as a walnut, but the writer has discovered one, left in situ in a streambed, roughly a cubic meter of black rock entirely unlike any surrounding boulders, and weighing many hundreds of pounds. This is likely to be a cultic object of the sort discussed by U-MN anthropologist Kevin L. Callahan: Petroglyph Boulders and Sacred Stones of the Upper Midwest ( -- the site includes a map of the distribution of these boulders throughout North America).

The pattern, size and number of concavities is not predictable, nor is material -- impressions are found in soft sandstone and hard granite. Cupstones may exhibit a mixture of large and small indentations, perhaps indicating multiple uses over a considerable span of time. Indentations range from barely visible (1/16" -- much too small for any use thus far hypothesized) to 6". In most cases the circumference of the impression will be roughly equal to the depth. Examination under magnification suggests the impressions were at least in some cases formed by rotary grinding. Typical impressions are of the simple pit type, though some cavities have been excavated to produce an opened-sphere type of pocket, by means and for reasons unknown -- as in the specimen immediately below (4.5" x 4"x3"; opening shown is .75" across, widening to 1" within). The object has another impression of equal width but only .25" deep. It also shows signs of use on two faces for grinding against a slab, the scratches indicating both linear and rotary motions.



A. approx. 13.5" x 8" x 6", 28 lbs., 32 impressions of various depth, ranging from 1/16" to1/2"

B. 9"x7"x3" This side is domed, and a flat, inclined surface may have been used for grinding or buffing. The cavity is 1.5" wide; the reverse --


-- shows an incised trench leading to or from the cavity (1.75"), suggesting that some sort of fluid was channeled into or out of the cavity. Incised lines are not uncommon; a spedimen recovered from the Big Eddy site had over 300 such lines, perhaps for drainage and drying of wet material.

C. 6"x 4" x 2.5" The cavity shown is 1" deep. On the back of the stone (in relation to the angle of the photo) is a much shallower impression of approximately equal width.

D. A large, irregular block of weathered sandstone, very subject to fracture (though observation of edge-wear indicates none of the breaks are modern), 7" x 7" x  4", 10 lbs. The dark spots to the left and right are connected in a sort of tunnel of varying width, incorporating a bend of about 100 degrees (the central dark spot is a trick of the light). The author speculates that it may have been used as a weight, perhaps to suspend provisions from a tree limb, out of reach of animals. It would make a practical anchor, though it was not found in a position likely ever to have been near water. The edges of the openings may show some slight degree of wear consistent with cordage. Below, the same stone shows a cluster of much smaller indentations (each about 1/4"). There is no reason but co-occurrence to assume a functional connection between the larger and smaller indentations.

E. This object, broken on the side away from the camera in relatively recent times from some larger body (unrecovered), could well have been used for grinding nuts or pigments -- the aperture is 1 7/8" wide and a full inch in depth. It might well be a mortar.

F. This flat specimen has fractured from some larger body, probably having originally had a bowl-shape. Again, the remnant, if any, was unrecovered; the author is not a trained archaeologist and does not dig for artifacts or remove them from undisturbed sites. The opening is 3.75" across, one of the largest observed by the author. The original depth of the cavity is unknown; the relatively flat surface around the opening shows signs of grinding or hammering.


However, the breakage did not necessarily end the object's useful life. The specimen below (G) is similarly broken at some layer of material weakness from a larger body, and on the smooth, upper side, there is a single impression. But on the opposite side, the rough portion originally inside the stone, later activity has added a second cavity, connected at a tangent with the first so as to make some sort of straining activity possible (shown a second time with contrast enhanced); a very small pit (1/8") is visible in the lower left quadrant, and a yet smaller one (1/32") about 1/4" inch to the right of the largest hole, in a line with the other two:


Both of the large indentations are of the spheroid type. On the side away from the camera, the rim of the single large opening is worn, and within the worn orbit are a number of pits so small as to be visible only under oblique light, and near the edge of the stone, another pit, drilled from a different direction, of 1/4".

Conclusion: function and terminology

The most likely interpretation seems that these artifacts represent a single technique of shaping or adapting stone for multiple purposes, some unguessed (for instance, the function of the smallest pits) and that the objects could be used by single or multiple individuals over long periods of time, and for various purposes. Indeed, the apparent randomness of their distribution may indicate that they were left lying as modified natural resources, whether with benevolent intent or because they did not represent a sufficient investment of time and labor to justify transporting them ("opportunistic" tools). More simply, perhaps the users intended to return to the same area during the next year's mast-gathering period. The now traditional term "nutting stone" may be justified, as may "straightening stone" or "shaft-anchor" within a larger class we might call "poculoliths," (<L. poculus, "small pocket," "cup"). While an equivalent to "pitted stone," the proposed term has the advantage of wider comprehensibility among international scholars as the worldwide distribution of the form becomes increasingly evident.

Links and information on poculoliths:

Publications and scholarship:

A professional study of coastal California specimens:

Fountain. "Cupped or Pitted Stones" The Archaeological Society of New Jersey Bulletin #52 1997 (113 pp.) $10.00 at

Peacock, Evan  1989  "Microdebitage from Cached Pitted Stones." Mississippi Archaeology 24(2):17-27.

Pyle, Robert L., "Mysterious Cupstones: A Secret of the Past," Wonderful West Virginia, July 1985

Ritchie, William A. Hammerstones, Anvils and Certain Pitted Stones (1929). Rpt. From Coyote Press (

Watts, Steve. "The Nutting Stone" The Bulletin of Primitive Technology Spring 1997 (The Society of Primitive Technology: SPT Bulletin #13: Foods and Cooking). Available at

J. Witthoft. "Pitted Stones and Cup-Shaped Markings." Publications of the Archaeological Society of Maryland. Volume 5, #2 (September 1969).

Images and commentary on the web:

A specimen found in Caithness, Scotland:

Discussion of a find near Jerusalem, with commentary on the possibility -- highly controversial -- that chimpanzees also engage in such activity, maintaining toolkits of suitable nutting stones over time.

See also Goren-Inbar, N., et al. 2002. "Nuts, nut cracking, and pitted stones at Gesher Benot, Ya'aqov, Israel." Proceedings of the National Academy of Sciences 99(Feb. 19):2455-2460. Abstract available at

Examples of central Texas stones associated with pestles. Dealer/owner believes the pattern of impressions on some of these stones is explained by gripping-points for fingers and thumb.

An impressive multi-pitted specimen from Indiana.

Diagram of a Connecticut specimen.

"In many parts of the world this type of artifact is usually associated with fall occupations."

Photo of a Massachusetts specimen:

An unusual, squared specimen from Madison Co. MS: stone

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