Indian Grinding Stone a/k/a Mortar

By

Andrew J. Myers

Introduction

In the summer of 1991, while conducting Phase I archaeological reconnaissance for the Ridgway Ranger District office of the Allegheny National Forest, the discovery of a small rockshelter was made high in the hills above the Clarion River valley in Elk County, Pennsylvania. While preparing to photograph and subsequently test the site for evidence of prehistoric occupation a rather unique feature was discovered within the rockshelter. Found carved into a table like rock was an intact prehistoric grinding stone a/k/a mortar.

While the number of rock-shelters found scattered across the Allegheny Plateau in northern Pennsylvania is large, very few contain intact features, especially those that lay hidden away and preserved from the destructive hands of vandals and/or the natural processes of weathering.

The site was subsequently recorded by the author into the PASS files at the Carnegie Museum of Natural History in Pittsburgh as Wingates Rockshelter (36EL82) named for a forester that worked at the Ridgway Ranger District office at the time.

Mortar features are associated with the grinding and crushing of food sources such as corn, nuts, seeds, and possibly ceramic tempering agents, and have not been commonly reported from rockshelter type settings in the region. This is the only rockshelter mortar known by this author from the upper Allegheny region although others probably exist.

Site Setting

Wingates Rockshelter (36EL82) is located on a ridgetop overlooking the Clarion River valley in the remote southwest portion of Elk County, PA. The nearest village of any size is the ghostown of Arroyo located some 3/4 of a mile to the southwest. Arroyo was once the setting of a sizeable tannery and now consists of only a handful of permanent residents and seasonal hunting camps.

The topography of this portion of the Clarion River valley is included in the Pittsburgh Low Plateau Section of the Appalachian Plateaus Province. Bedrock at the elevation of the rock shelter corresponds to the Pennsylvania Pottsville Formation Pottsville Sandstone. The site is positioned at the 1529' elevation along the edge of a narrow saddle found connecting the end of a long lobate ridge located well above the Clarion River valley below. While the location of the rockshelter seems remote by today’s standards it was likely one of a number of rockshelters used along defined trail systems. The canoeable Clarion River road passed directly below the site and the rockshelter is ideally positioned and included in a proposed trail described by the author (see Myers 1997:51; Trail 1) that has antecedants well north of the site. This proposed trail originated at Buckaloons (and points northward) and traveled through the Tionesta Creek drainage before entering the Clarion River drainage on it’s way to the West Branch of the Susquehanna passing directly below Wingates rockshelter. Certainly the density of rockshelters in the vicinity of Wingates rockshelter attests to the significance of the trail system.

36EL82 Wingates Rockshelter looking southeast

The rockshelter that holds the mortar is quite small by local standards. General measurements are 7 meters north south by about 3 meters east to west. The space from backwall to dripline measures around 2 meters. The height of the rockshelter ranges from around 6 feet in the northern end to perhaps as much as 10 feet along the southern end. The rockshelter faces approximately 40-60 degrees northeast and is open 140 degrees SE and 320 SW. The habitation floor of the site is small with only some 10 square meters of clean living space being found underneath of the overhang. The majority of the northern end on the overhang is filled with talus including in the general vicinity of the mortar.

Field Sketch Map Wingates Rockshelter

Water sources are unknown from the immediate vicinity of the site. Springs are likely located along the base of the slope below the site but these have yet to be located. Cole Run is the nearest drainage located some 700' nw of the site while the Clarion River is located some 800' southeast of the rockshelter. To reach either drainage a steep descent downward to the valley floor is required with the slope down into Cole Run being slightly more gradual that the steep drop off to the Clarion River. Relief from the rockshelter to the valley floor is some 240'.

Profile view of the site looking northwest

The mortar was carved in a rock found located under the protective portion of the overhang. The rock most likely did not shock from the ceiling but was one of a number of rocks found strewn as talus slope on the extremely rocky eroded hillside. The flat and soft nature of the sandstone slabs were probably key variables in selecting the particular rock for a mortar.

The mortar while located near the old dripline was not formed by running water. The main feature is too deep and too perfectly formed to have been done through natural weathering.

Dimensions

The mortar is made up of of two and perhaps as many as three individual grinding areas, two of which are now broken. The main mortar is circular in shape measuring some 17 cm in diameter. The mortar measure 18 cm north-south by 16.5 cm east- west. The mortar measures 9.5 cm in depth and is deepest near the center. Located just 2 cm sw of the main mortar is another now broken mortar. This mortar is 6 cm north to south by 11 cm east to west and now measures 6.5 cm deep. The remaining portion of this mortar is missing. A third mortar may also have been carved into the rock and is now only represented by a rounded polished arc. The rock apparently cracked on occasion resulting in the locating of new milling station periodically.

Mortar Uses

Mortars were used for grinding purposes. In this part of the country, acorns and other nuts types found on the hilltops, seeds, and possibly tempering agents such as quarts and mussel and clam shell to be added to the ceramic paste of pottery were likely in these feature types.

Cultural Affiliation

It would be hard to place a cultural affiliation on a feature of this type. Testing conducted at the site did produce evidence of Woodland occupation in the form of prehistoric ceramics. The earliest Early Woodland group produced thick grit tempered Half Moon Cordmarked pottery while the later group visited the rockshelter many years later during the Late Prehistoric period and produced thin shell Chautauqua Cordmarked like ceramics.

Chipping debris was conspicuously absent during testing suggesting that the site was occupied primarily by woman who were grinding nuts such as acorns and manufacturing pottery.

Rockshelters occasionally produce features associated with the processing of food resources. At the Dameron Rockshelter in Johnson County, Kentucky(Vento et al 1980: 94-98) a number of pitted boulder size stone were recovered. The majority of these appear to have been used as nutting stones. Nutting stones were also recovered from the Khone Rockshelter found by the author along the Lost River in Hardy County West Virginia while employed by Michael Baker Jr., Inc.

Other Mortars

The finding of an intact mortar is rare. The local history books often speak of these features but whether these accounts are factual or simply folk lore remains uncertain. Harry Hill, a former police chief of Ridgway, Pennsylvania, reported in his history of Ridgway entitled “The Story of Ridgway” that a mortar was discovered in a rock found along Big Mill Creek (Hill 1964: 1) located just west of Ridgway. He speculated that corn was ground on the rock. Big Mill Creek is located only a few miles east from Wingates Rockshelter. This author has not seen the mortar described by Hill and knows of no one who could locate the feature. Mr. Hill has long since passed.

Mortar pictured (bottom left)by Harry Hill in The Story of Ridgway and found along Big Mill Creek

Recently another possible mortar site was brought to the attention of the author by a local informant Mr. Desmond. The site known as Millstone Creek Milling Station, located on Allegheny National Forest property, has recently been recorded into the Pennsylvania Archaeological Site Survey (PASS)files at the Carnegie Museum in Pittsburgh and with the Bureau for Historic Preservation in Harrisburg, as 36EL209. This particualr site is located just east of the village of Lamonaville in the Millstone Creek drainage of Elk County. The site consists of several mortars (40+) that were carved in a grouping of three flat table like rocks located well above the present drainage course of the East Branch of Millstone Creek. They do not appear to be natural potholes caused by hydraulic drilling but rather purposefully made. The author has subsequently photographed the site and some of these will be made available at this website.

Mortar east of the village of Lamonaville in Elk County, PA

Another possible rockshelter mortar was discovered while photographing the Maple Creek Rockshelter (36FO68)located on the hillslope above the Clarion River near Clarington in Forest County, PA.

Possible mortar feature found at the Maple Creek Rockshelter located near Clarington in Forest County, PA

The Maple Creek rockshelter is very small with only about 6 meters of living space accounting for the entire site area. The ceiling of the overhang is approximately 1 meter high. Basically there was enough room for one or two few people who built a hearth and then possible ground a mortar into a rock found underneath of the overhang. The mortar itself is approximately 6 cm in diameter and 2 cm deep.

Maple Creek Rockshelter(36FO68)

Additional information on bedrock mortars will be presented as it become available.

References

Hill, Harry M.
1964 The Story of Ridgway. Ridgway Publishing Company. Ridgway, PA.

Myers, Andrew J.
1997 An Examination of Late Prehistoric McFate Trail Locations Pennsylvania Archaeologist 67(1):45-53.

Vento, F. J. et al.
1980 Excavations at Dameron Rockshelter (15JO23A)Johnson County, Kentucky. Ethnology Monographs Number 4, Department of Anthropology University of Pittsburgh.