Crucibles For Casting Found At Cahokia?
Neiburger's Evidence: Native Americans
Melted, Cast Copper at 1,000 BC Site
Scientific evidence of prehistoric Indian copper casting was published in an article in North American Archaeologist, written by an Evanston, IL dentist, Ellis J. Neiburger, a man who became interested in metallurgy while in dental school. The title of Neiburger's paper is "Melted Copper From the Archaic Midwest," 1991, V 12-4, Baywood Publishing Co., Amityville, NY. This paper offers xeroradiographic proof of ancient casting. All of Neiburger's photos and images which appear in this web site are: Copyright, E.J. Neiburger, 2001. His 1991 paper contains important evidence of prehistoric copper melting and casting.
Describing this copper artifact from an archaeological site in Menominee County, Michigan, Neiburger said it is "a large lump of documented copper" from the 1000 BC Riverside side just north of the Wisconsin state line. The lump weighs 5407 gm and is 6.1 cm long, 4.1 cm wide and 0.8 cm thick.
This xeroradiograph of the Riverside copper lump shows numerous large, ovoid radiolucenties grouped in clusters. This indicative of melting in which gas bubbles, trapped in the molten metal, will cause porosity as the artifact hardens. Hammered (unmelted) or natural float copper will show faint elongated voids where laps and folds in the metal occur. In the R666 lump, however, one sees aggregate porosity indicative of casting.
Photomicrographs (200x) of (FC) cast and hammered float copper, (prepared by author), on left side, is compared to that of the R666 Riverside sample, on the right side of the image.
The abstract of this article says that: "A large lump of documented copper from the 1000 BC Riverside, Michigan site was found to posses internal porosity and a microstructure indicative of casting and hammering as the means of manufacture. Prior to this discovery, Archaic Native American Indians were considered technologically primitive and incapable of possessing the high heat technology necessary to cast metal."
Neiburger's article thus offers photographic proof of small voids in the 1000 BC copper artifact. These would only form as bubbles of gas in molten copper. Also in his article he points out that the Great Lakes native copper deposits were not the result of the cooling of molten lava, but were rather deposited by geologic precipitation about one billion years ago. Thus the native metal would contain no such gas voids.
So far the Riverside lump is the only such artifact from a well documented site known to Neiburger which shows clear evidence of prehistoric casting. Other artifacts examined by Neiburger and found to have evidence of casting are surface finds, and therefore not completely conclusive, because of the possibility that they are modern copies of Indian artifacts.
An example of evidence of casting in a surface find can be seen in Neiburger's xeroradiograph of a copper celt from the Perkins Collection of the Milwaukee Public Museum, Milwaukee, WI. A photo of the celt is on the left and the xeroradiograph is on the right. The casting bubble can clearly been seen near of the middle of the wide end of the xeroradiograph of the celt, right:
Commenting on the need for further testing, Neiburger said "Further xeroradiographic surveys and analysis of the 25,000 existing copper artifacts from that period (Archaic Midwestern United States) are necessary for the determination of how extensively early Native Americans had used melted metal."
Seeking more answers to the question of whether or not prehistoric North American Indians cast copper, recently I wrote to Dr. Ellis Neiburger, who seems to be one of the world's most knowledgeable amateur archaeo-metallurgists in the field of copper casting.
As it turns out, after a telephone conversation with him, I've learned that much of his knowledge comes from his hobby of metal casting. He is the operator of a so-called "backyard foundry," and has been for many years. He told me he has made over 2,000 castings.
Neiburger, of Waukegan, Illinois, has enlightened me on some things he has learned which I am using to revise this web page. I'm sure his input will lead to a better understanding of the issues involved in our project to examine and evaluate evidence of prehistoric copper casting in North America.
He pointed out to me, for instance, that evidence suggesting the use of casting such as surface depression or concavity, large size and symmetrical form are not by themselves fool-proof evidence of prehistoric casting. This calls into question evidence of casting cited by Arlington Mallery and Earle Caley 50 years ago, which is discussed further on in this section of "America's Mysterious Furnaces."
Also, and equally important, he said any copper artifact considered for xeroradiographic testing should first be subjected to a specific gravity test. If the artifact is found to weigh less than an equal volume of native copper, the presence of casting voids is indicated. The Riverside lump R666 was first given a specific gravity test. After it tested less (8.2) than native copper (8.9), Neiburger had the xeroradiograph made shown above.
Could Radiographic Tests Of Large Copper Artifacts
'Revolutionize' North American Archaeology?
Inconclusive Test Was A Result Of Discussion By Internet E-Mail Group;
Author Of This Site Was Unable To Have Larger Artifact Tested
A program of Radiographic (X-ray) testing of large copper artifacts to seek evidence of casting should be conducted to determine if any prehistoric North American artifacts were made by casting! An unsuccessful test was made by the author of this web site, but unfortunately, the artifact selected for the test was, in my opinion, too small. While large prehistoric copper artifacts are valuable, and while those in charge of such artifacts are reluctant to send them away for testing, failure to conduct such tests in my opinion is just unscientific.
This project came about a result of the author's participation in the Arch-Metals e-mail discussion group. Some Arch-Metals members agreed recently, after a prolonged discussion, that most large, prehistoric copper artifacts had been cast nearly everywhere in the prehistoric world except in North America.
At this point in the discussion, I posted the fact that North American copper artifacts had been tested by X-ray imaging and the results, which were published 50 years ago by Arlington Mallery, showed evidence of casting. But somehow the opinion that North American Indians never cast copper had become a "fact" among professional archaeologists. One member of Arch-Metals, who responded to my posting of Mallery's test results, asked why they had never been republished and said that if North American prehistoric copper artifacts are found to have been cast, it could "revolutionize" North American archaeology.
I established the "Early Caley Research Fund" to pay for the cost of a program of prehistoric North American copper artifact testing for evidence of casting. Dr. Martha Otto, curator of archaeology of the Ohio Historical Society Museum of Columbus, and the author of this web site, conducted the test. I also consulted with Dr. David Scott of the Getty Conservation Institute, Getty Museum, Los Angeles, CA. At the time, I had serious reservations about the small size of the artifact chosen for testing. And, unfortunately, the test conducted by the Getty for Dr. Otto indicated the small copper celt had been formed merely by cold working.
The 28-pound Seip Mound Celt Of The Ohio Historical Society Museum
Evidence Of Prehistoric Copper Casting
Endorsed By Caley Nearly 50 Years Ago
Although archaeologists today seem united in their view that large prehistoric North American Indian copper artifacts were not cast from molten copper, amateurs have been finding evidence to the contrary for many years and their findings have been supported by metallurgists.
For instance, amateur Arlington Mallery's studies of prehistoric copper use by native Americans of the Great Lakes region convinced him that they melted copper and cast it into axes, chisels, spearheads and sheets. This conclusion received favorable comments from some American professional archaeologists of the 1950's.
The widely accepted theory that the native North Americans used copper only as malleable stone is wrong, Mallery declared, because many of the heavier pieces, such as axes and chisels, had never been touched by a hammer except at the cutting edge. Therefore, he concluded these pieces could not have been hammered out of material from the naturally occurring native copper deposits, but would have had to have been cast from molten copper.
50-Year-Old Evidence of Prehistoric North American Copper Casting
As Mallery pointed out in "Great Lakes Copper Culture," an appendix in The Rediscovery of Lost America, micrographs made of samples of these prehistoric objects indicated that the copper had been melted in an open crucible. Tests showed that surfaces of these copper artifacts were impregnated with cuprous oxide, and Mallery said this proved that alloying with oxide during melting had occurred, to produce copper artifacts which are harder and more brittle than pure Great Lakes copper.
He reasoned that objects made with this pure, native metal would not have cuprous oxide on their surfaces if shaped simply by hammering. Formation of the cuprous oxide would occur only while the copper was molten, reacting with the air to produce the alloy.
According to Mallery, an indication of the degree to which the native Americans were involved in the production of artifacts of copper can been seen in the fact that over 100,000 copper objects, such and tools and ornaments, have been found in North America. As he said in Lost America, if only a small percentage of the many thousands of copper objects made by the Indians were accepted by archaeologists as being made from cast copper, the whole theory of a stone age pre-Columbian North America must be rejected.
Dr. Earle E. Caley, then a professor of chemistry at The Ohio State University, reviewed the metallurgical content of Lost America as part of an evaluation of the book by five OSU professors in the Ohio State Archaeological and Historical Quarterly, July 1953. All but Caley had nothing much positive to say about Mallery's conclusions. Caley, while not in agreement with Mallery that the pit furnaces were iron smelters, was in agreement with him about the copper casting. Caley said, "the technical evidence he presents for the existence of the practice of melting and casting copper at an early date in North America is important and appears to be both sound and adequate..."
This is a very strong endorsement, running against the grain of what the other OSU professors said about Mallery, but it seems to have had little effect. Caley in 1953 was already a published archaeo-metallurgist, and later became noted for his studies of the pre-Inca Moche Indians of Peru, who smelted copper from the ore beginning in 200 AD.
In the 1950's, evidence of such copper ore smelting in South America was just beginning to be scientifically studied, and Caley's conclusions in "The Smelting of Sulfide Ores of Copper in Preconquest Peru" were controversial. But during the1980s, much more evidence came to light, especially with the publication of "Batan Grande: A Prehistoric Metallurgical Center in Peru" by Izumi Shimada, Stephen Epstein and Alan K. Craig in Science. Shimada, Epstein and Craig reinforced Caley's earlier work, showing that the pre-Columbian Indians of Peru did indeed smelt sulfide and oxide ores of copper.
To my knowledge, Caley never reversed his positive evaluation of Mallery's evidence of copper melting and casting by North America's pre-Columbian Indians. It is really strange that no American archaeo-metallurgists have seen fit to follow up on this.
Quite likely, they've never been made aware of it. So today, our archaeology textbooks still read that the North American Indians did not know how to melt and cast copper. But if the metallurgical tests cited in Lost America are accurate (as conducted by a disinterested commercial laboratory) there is no question that the tested artifacts were copper castings.
While much of what archaeologists study consists of only of rather enigmatic artifacts and habitation sites, which may shed little direct light on the cultures of its origination, the technological evaluation of metals involves physical science and thus is quite straightforward. Such evidence needs little of the creative interpretation which they of necessity must apply to other prehistoric evidence. So it is difficult for those who wish not to accept such evidence to argue against it, but it has been quite easy for them to just ignore it.
Indeed, I know of no published technical refutation of Mallery's claims about the Indian copper casting as published in his books. Mallery tells us that at the suggestion of Matthew Stirling, then director of the Bureau of American Ethnology of the Smithsonian Institution, he examined copper artifacts of the Perkins collection in the National Museum of Natural History. Mallery says right away he noticed that there were "a number of castings in the collection." Further, he states that "there are similar castings in nearly every museum in America." And, he says "expert foundrymen who examined the Perkins collection of the Wisconsin Historical Society declared that many of these specimens were cast in a mold."
And, after examining the results of Mallery's test of prehistoric copper artifacts, Dr. George Ellinger of the National Bureau of Standards said, "The centers of some of these chisels were decidedly depressed or concave. This is caused by the decrease in volume (or shrinkage) of the molten metal upon solidification. It is a common phenomenon well known by all foundrymen and those connected with the melting and casting of metals. This concavity is more or less pronounced in many of the ancient specimens and particularly so in the pentagonal chisels."
Chisels, spearheads and axes were among the prehistoric North American artifacts Mallery had tested for evidence of casting 50 years ago. The above comments by Ellinger also appeared in "Appendix A, Great Lakes Copper Culture," of both Lost America and The Rediscovery of Lost America.
Mallery's expertise with metallurgy came from his occupation as a pioneer steel bridge builder. As a registered professional engineer, he designed and built many highway bridges in the 1920's and 1930's. But his expertise in metallurgy wasn't matched by his knowledge or use of archaeological methodology, and this made it easy for his critics to dismiss all of his work, both the good and the bad. Mallery was, very simply, not very good as an archaeologist.
But since metallurgy is rather straightforward, Mallery, Stirling and Ellinger must have been surprised that the American archaeological community of the day was unresponsive to the news about casting, despite what seemed to be an "overkill" of pro-casting technical evidence.
Archaeologist Was Confused About 'Smelting'
The opposition of American archaeologists to ancient American copper casting is reflected in an otherwise excellent booklet Miskwabik: Red Metal, The Roles Played by Michigan's Copper In Prehistoric North America published in 1983 and written by John R. Halsey, state archaeologist of Michigan. Halsey says in his book "Of one thing we are certain: no native copper was deliberately smelted. Metallographic analysis of numerous copper specimens from eastern North America has not found telltale changes in their internal crystalline structure that would have occurred if metals were heated to their liquid state to remove their impurities."
With this statement Halsey deserves a failing grade in Metallurgy 101 since he thinks native copper needs to be smelted and that impurities need to be removed from pure copper! Also, I'm sure a collection of thin copper artifacts could be assembled to "prove" no Indian copper artifacts were ever cast.
Mistaken, unscientific opposition to evidence of ancient American copper casting is not harmless! A privately owned site such as Spruce Hill in Ross County, Ohio is always in danger of destruction. Indeed considerable destruction has already occurred there. But much evidence remains, which could be highly useful to our understanding of the evidence of ancient metallurgical processes at this important site.
Still abundant there is evidence of the use of charcoal fueled furnaces to achieve temperatures and conditions which permit the creation of multicolored iron oxide glazes on rocks. Carbon-14 and thermoluminescence tests of such materials, could reveal when these furnaces were in operation. Then perhaps Spruce Hill, which has already been considered, could be included in the Hopewell Culture National Park of the US Park Service and the site could be recognized as a center of ancient metallurgical industry.
A Mold For A Hopewell Copper Celt?
The Cahoon Mold
The lump of heat-hardened clay above was found at Spruce Hill near Bourneville, Ohio by John Cahoon on April 25, 1993. Spruce Hill is a 140-acre plateau enclosed by a prehistoric wall of laid-up stone attributed by archaeologists to the Hopewell Culture (200 B.C. to 400 AD). Cahoon, owner of an orchard which adjoins the site, was with members of the Archaeo-Pyrogenics Society (APGS) on a field trip when he found the lump.
Cahoon found the mold in a rain-filled bulldozer trench in "the isthmus" area of Spruce Hill where ancient furnaces were located. On the day of the field trip, about an inch of rain fell which may have dissolved softer soil from the mold. The object weighs 13.5 pounds. The cavity of the Cahoon mold is about one-half inch deep, two inches wide and six inches long. It widens somewhat at the end facing the ruler, suggesting it perhaps was used to form an elongated celt. Vitrified clay on both sides of the cavity bear witness to the intense heat of the material in the mold. The clay of the mold looks like bog iron ore, and in fact, Cahoon described it as "an ore body."
The author of this web site has researched copper metallurgy and Native American artifacts made of copper for many years. I've suspected that the Cahoon Mold was used by ancient Indian metal workers to cast a copper celt. But was the Cahoon mold used by Hopewellian Indians to cast copper as I have proposed?
Maybe not. Replying to my posting about this on Arch-Metals, the archaeo-metallurgy Internet mail list, Chris Salter, of the Materials Science-Based Archaeology Group, Oxford, U.K. replied:
I am sorry but I have to agree with the others that have said that the material illustrated is not a fragment of a mould. Having examined several hundred mould fragments from all periods, none look like the material illustrated.
It is difficult to determine what the material is from a single image, but the most likely origins are as a hearth lining, or the result of an uncontrolled fire in a timber and clay building (I have seen similar vitrification in the walls of timber-laced ramparts of British hill forts, and on a stone built charcoal store).
The essential features required to produce such vitrification appear to be a sufficient supply of fuel, and flue ventilation (good air supply at base, and venting at top, with some mechanism to create a forced draught (be that height of flue, or wind).
Another viewer of the Cahoon Mold, Wes Clark replied:
Your speculations and information connected to a possible prehistoric copper celt mold are very interesting. I have a suggestion, however. Could you provide a better photo of the "mold"? A lab photo with oblique lighting would show better detail. The present photo shows to some extent the morphology you contend is a mold for a celt, but is still a little too amorphous for my taste.
Dr. Neiburger, however, a man who has made some 2,000 castings, believes the "Cahoon Mold" could have been used to cast a copper artifact and has suggested it be tested for traces of copper.
If the Cahoon mold is not the remains of a copper casting mold, but is a prehistoric Hopewellian artifact, it is still remarkable because of its rectangular shape. Were these Indians sophisticated carpenters who made use of square boards or posts? Is the Cahoon mold an accidental impression left by a burned away prehistoric board or post? Was this impression made by a post used to support a wooden palisade at the top of the fort's walls?
Fire Pits or Furnaces, They Remain A Spruce Hill Mystery
Spruce Hill, the "Ancient Stone Work" as mapped in Ancient Monuments of the Mississippi Valley by Squier and Davis, has attracted generations of archaeologists to its plateau enclosed by walls of loose stone. The purpose of the many mysterious fire pits or furnaces found in the walls has long been a mystery, as has the existence of "the fort" itself.
Although the Cahoon mold may not be the "smoking gun" evidence of copper casting, conclusive evidence needed to solve mystery of the Spruce Hill furnaces may still exist somewhere at the site. And, because of other supporting evidence, I'm still convinced some sort of prehistoric metallurgical operations were conducted there.
The furnace remains were first reported in 1811 by James Foster, editor of the Chillicothe, Ohio newspaper. He was asked to view the site by local residents who were astonished by its existence.
Foster reported seeing "about 30 furnaces" in the Spruce Hill walls upon which huge trees were growing. This implies that the furnaces were at least hundreds of years older than 1811. Foster's Spruce Hill observations were reported in a letter found tucked inside an 1814 book, the American Medical and Philosophical Journal.
For more information on Spruce Hill and its furnaces, go to Ohio's Prehistoric Furnaces this web site.
Did Native North Americans Cast This Celt?
The affirmative answer to this question came during a 1992 interview with Carroll Mobley, professor of metallurgical engineering at the Ohio State University. David Orr and I, representing the APGS, requested a meeting with the professor to discuss metallurgical questions posed by our investigation of Ohio's mysterious pit furnaces. When questioned about the copper controversy, the professor told Orr and I that the large Seip celt on display at the Ohio Historical Society Museum in Columbus is evidence of copper casting because it is a copper casting!
The Seip Mound celt in its display case at the Ohio Historical Society Museum.
Mobley in 1992 said he is amused every time he passes by this artifact because archaeologists believe it was created by some means other than melting and casting. Metallurgists passing by the celt know better he said, because native copper's malleability is limited. While small copper nuggets can be hammered into thin sheets of copper, the professor said it would have been impossible for prehistoric Indians to shape copper into such a massive and symmetrical piece as the 28-pound celt or ceremonial axe above. (Photo by Bill Barr)
However, now in 2001 I find that Dr. Neiburger isn't as sure of this as Mobley was. He has examined other celts of comparable size, well documented to be prehistoric, and found evidence of hammering and annealing, but none of casting. He said the smooth and symmetrical shape could have be attained by hammering, annealing and the use of abrasive materials. It is also the case that such "cold working," if applied to artifacts that were originally cast, could obliterate evidence of the casting.
The size of the Seip Celt is illustrated by the arm of James Leslie, Barr's assistant. His hand is 4" wide and his arm is 17" from middle fingertip to elbow. The elongated shape of this celt or axe suggests a purely ceremonial or symbolic purpose for the artifact. Was it an indication of a community's wealth or prosperity?
Seip Mound is part of the Seip group of mounds, located in Ross County, Ohio in the Paint Creek valley, five miles upstream from prehistoric Spruce Hill where the Cahoon Mold was found.