Square

Squared Stone Fragment Found
At Spruce Hill Works in Ohio
By William D. Conner

Two views of the fragment of Berea sandstone, above, show how three plane surfaces converge to form a corner. The image on the left shows this convergence. The image on the right shows that a corner of the fragment is missing. This irregular fragment is about 3.5 x 2 x 1.75 by measuring its longest sections, and weighs 10.5 ounces. It rests on 1/4-inch grid paper. While it might not be visible in the photos above, the surface just above the knocked off corner seems to be a deposit of clay mortar. None of the natural red bands in this artifact are level or are otherwise configured such in a geometric position. (Photos by author)

This close-up of the same fragment shows red bands of the sandstone and the extent to which its upper surface is covered with a darker material. The author suggests this might be the remains of clay mortar. For the furnaces of the SHW to produce celedon glazes on sandstone, or hard-baked mortar as shown above, metallurgical temperatures had to have been achieved in them. The furnaces, therefore, would seem to require some form of stone masonry (if only roughly worked sandstone blocks cemented together with clay) to contain hot carbon monoxide gas. This would maintain furnace reducing conditions to produce the celedon glazes that are still in evidence on some SHW stones. The sandstone itself is highly refractory (resistant to melting), so glazed surfaces on stone fragments at the SHW must have come from the clay which is less refractory.

Discussion

A piece of Berea sandstone with a squared off corner, obviously a fragment of a larger object, was found Spruce Hill Works (SHW) in Ross County, Ohio by the author of this web site during an April 2003 visit. The fragment was lying in a bank of rubble just below the place marked as "Point F" on the Squier and Davis map as published in their 1848 book "Ancient Monuments of the Mississippi Valley." At Point F, Squier and Davis reported finding vitrified stones fused together and other materials which they said were evidence of the effects of intense heat. Since this fragment seems to be evidence of stone masonry at SHW in prehistoric times, it also relates to the Squier and Davis report of seeing "some arrangement in the stones, tending to the belief that the wall…may have been regularly faced upon the exterior."

The Berea sandstone formation caps the 300-foot elevation of the Spruce Hill plateau’s slopes. Because some pyrogenic materials found at the SHW have Celedon glazes, only formed inside high temperature furnaces capable of producing reducing conditions, one should expect to find some evidence of masonry, including the use of refractory mortar needed to hold it together.

Indeed, the "30 furnaces" reported by Foster must have been still sufficiently intact for this investigator to report them as such. The existence of such "furnaces," therefore, presumes the use of stone masonry joined by refractory mortar, since no brick has been found at SHW. And, indeed, the use of refractory clay mortar in SHW materials is evident in other rock fragments this writer has found at the SHW.

While I have always been reluctant to remove materials from the SHW, because of its importance and significance, I collected this artifact for further study and comparison to other Spruce Hill archaeo-pyrogenic materials. I am very interested in establishing the great importance of this site as a means of obtaining funding for its purchase and addition to the Hopewell Culture National Park system centered on the city of Chillicothe, Ohio.

Any other visitor to this site might not have recognized the importance of this artifact. However, since I have already found other evidence of the use of stones in the construction of the Spruce Hill furnaces (first reported by Foster in the early 19^th century), I have been looking for evidence of stone masonry. It has been said it is difficult to find what you aren’t looking for, and in this case, the reverse was true. I was looking for an artifact like this and now have found it.

I know of no other rock fragment from Spruce Hill that shows such clear evidence of masonry. Hugh McCulloch, who accompanied me on this visit, used a GPS receiver to fix the position of the spot where the squared stone fragment was found and also other features of the SHW. The squared stone fragment was found on the property of Tommy Shoemaker of Chillicothe on the west side of the SHW, across the Paint Creek valley from Bourneville. The SHW is on the list of properties Archaeological Conservancy would like to acquire if funds can be obtained.

The fragment I found is only one piece. I didn't look for more because other explanations for its presence seem far outweighed by the odds that it is as old as the rest of the SHW. Convergence of three plane surfaces on a piece of sandstone into a corner doesn't occur in nature. Only natural crystals have such converging plane surfaces. Sandstone does not form crystals (Peterson Field Guides Rocks and Minerals, Frederick H. Pough, Houghton Mifflin Co., New York, 1983). So this fragment has to be man-made. Can I prove it is ancient? No, but this seems to me the most likely explanation for its presence.

Also, some might object that this piece is "only a surface find." Well, what's left of the SHW enclosing wall is one big "surface find" as are pyramids, mounds and other earthworks. It is well-known by folks whose families have lived around the SHW for generations that stone was removed from the SHW walls by the wagonload and used as foundation stones for barns, houses and other buildings. Some of this could have been cut and squared at the SHW before being hauled away.

However, the layer of clay mortar on this stone seems to be proof it was squared before being used in an ancient structure at Spruce Hill, either as a part of a wall, or, as a part of a furnace built into a wall. Clay mortar was used in ancient furnace structures because it is highly refractory (heat resistant). Brick clay is used for mortar in brick kilns and in metallurgical furnaces because ordinary lime mortar cannot withstand the intense heat. In modern masonry, special heat-resistant mortar made with burned clay is used for the fireboxes of fireplaces. Also, smaller mortar joints, about 1/4 inch, are used between firebox bricks.

My first experience as an archeologist with clay mortar came in 1992 when David Orr and I excavated a pit iron furnace in Pickaway County's Salt Creek Township near Laurelville, Ohio. The same clay used to make the bricks at the Lynn Acres Furnace was also used as mortar, with the mortar averaging about three-eighths of an inch thick. I learned then brick clay was used for mortar because ordinary lime mortar could not withstand the intense heat of the furnace.

Use of clay mortar in a lime kiln is mentioned in "Archaeological Investigations at the Rudd Lime Kiln, Livingston County, Kentucky," by Charles D. Hockensmith. In this 1966 report, Hockensmith discusses the use of clay mortar in the brick masonry of the 19th century kilns. He says the struck surface of a brick found at the site "has an irregular (5x 10.5 cm) layer of clay (ca. 8 mm thick) adhering to it. This layer of clay has a gray glaze covering a portion of it upper surface. It is not known whether the clay was used as a mortar between the bricks or if this was excess clay that stuck to the brick during its manufacture. This clay adhering to the brick may be a special refractory clay used as a mortar."

While this report of evidence of clay mortar use at the SHW is mine alone, a US Park Service publication reported finding evidence of faced stone work there in 1995, when several excavations were made by archaeologist Bret Ruby. This was reported in Research at the Spruce Hill Works as follows: "...we found that the bulk of the enclosure was constructed of small, rubble-sized stones, with the outer surfaces being faced with larger blocks, perhaps to stabilize the structure."

References:

Archaeological Investigations at the Rudd Lime Kiln, Livingston County, Kentucky; by Charles D. Hockensmith, Ohio Valley Historical Archaeology; Journal of Symposium on Ohio Valley Urban and Historic Archaeology; pp. 115-124; v. 11; Louisville, Ky., 1996.

Gurcke, Karl. Bricks and Brickmaking, A Handbook for Historical Archaeology. University of Idaho Press, Moscow, Idaho; 1987.

Masonry Skills, Richard T. Krek, Sr., Delmar Publishers, New York, 1990.

Research at the Spruce Hill Works, article in The Falcon, The Newsletter of the Hopewell Culture National Historical Park, Fall/Winter 1996-1997, Chillicothe, Ohio.

Rhodes, Daniel. Kilns, Design, Construction and Operation, Chilton Book Co., Radnor, Pa., 1968.

For further discussion of evidence of the use of SHW furnaces for melting and casting copper artifacts by prehistoric native Americans, and evidence found at other sites, use these links:

Ohio's Prehistoric Furnaces

Copper Casting In Ancient America?

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"Squared Stone Fragment Found At Spruce Hill Works in Ohio"

Posted 4-8-03; revised 4-30-03.