You may wonder why the science of geology is all that important to the study of the rune stone and whether it matters what kind of stone it is. In fact, the first real champion of the stone was the Minnesota state geologist, Newton Winchell. He conducted an extensive study in 1909-1910, that determined the type of stone and that it was native to Minnesota, and studied the topography of the hill on the Ohman farm where it was found 12 years earlier. Winchell also conducted extensive interviews with everyone present at the discovery and those who knew them. He concluded in a report both comprehensive and eloquent, that the Kensington Rune Stone was a genuine medieval artifact. Winchell was one of the giants in KRS history. His thoroughness and dedication to objectivity and accuracy stand in marked contrast to some other figures who have written about the rune stone. The science of geology has changed a lot in 100 years, but the work done in recent years, principally by Scott Wolter has been largely a replication of Winchell's work employing new technology.
The purpose of this page is to give the reader an overview of the key areas of geologic study on the KRS, and what geology tells us today. First, a few words about the stone as its carver found it. The carver selected a large flat stone, presumably near the Ohman farmstead, that had been deposited by glacial ice 12-15,000 years ago. The back side has up to 1/4” deep glacial scratches, parallel to the long axis of the stone, from glacial ice passing over the slab most likely when it was still a part of the bedrock.
The Split Side
We can presume that the KRS party looked for a stone of a general size and shape. They apparently found this stone suitable but too large, and an expert stone worker used his tools to split it in two. When you look at the face of the stone you can see the bottom left has a different appearance. This is known as the split side because it is a newly revealed surface created when the stone was split. The tool marks the stone cutter used to do this are visible. This entire surface has the same color, texture, and weathering profile as the original inscription, and is not as advanced as the glacial (original) surfaces on the rest of the stone which have a different overall appearance. This tells us the split side was made at the same time as the original inscription.
There are two, white, roughly ½” wide, undulating and branching lines running across the glacial back side of the stone that were produced by prolonged contact with tree roots. Such scars left on rock are relatively common and are produced by a symbiotic relationship between fungus in the ground and acid from the root that leaches nutrients from soil and rock as food for the tree. The root-leaching pattern matches the testimony of the twelve witnesses who signed written affidavits, and the three sketches made from first-hand witnesses (Olof Ohman in 1909, Sam Olsson in 1910 and Olof Ohman Jr. in 1957). Photo below.
Winchell noted in his report that Olof said he took a nail and scratched out the inscription which was still packed with mud. The nail crushed the minerals at the bottom of the grooves which then turned white giving the inscription a “fresh” appearance to the untrained eye. However, microscopic inspection shows the walls of the grooves exhibit extensive weathering. Many past investigators commented on the “fresh” appearing inscription and claimed it as evidence of a hoax which no doubt caused confusion and negative bias that continues today.
Pyrite, an iron sulphide, is present in greywacke stones like this, and is a mineral that weathers relatively quickly in the presence of water and oxygen. When it weathers it becomes iron oxide. Many small pits along the walls of the grooves are lined with iron oxide deposits produced when exposed pyrite crystals weathered away. The question became: how fast does pyrite deteriorate to iron oxide in an environment like that to which the KRS was exposed, and can that be used to date the cut and carved surfaces?
A fortuitous control sample for pyrite weathering was discovered in 2001, when a rune-inscribed boulder was found near the Ohman Farm that later proved to be a prank. The boulder was tested and found to contain pyrite of the same size as in the Kensington Stone. Actively weathering pyrite crystals were found within the carved grooves of the prank inscription that was made by archaeology students at the University of Minnesota, in summer of 1985. As of the summer of 2010, the pyrites in the prank inscription were still actively weathering. When compared with the completely weathered pyrite pits within the Kensington grooves, the conclusion is that the KRS inscription was subject to weathering for far more than 26 years. Since the stone has been protected from weathering since 1898, in order for the pyrite to have so completely weathered in the KRS inscription, it had to have weathered for far longer than 26 years “before” it was discovered, essentially ruling out a hoax.
Four different mica minerals are present in the Kensington greywacke. Mica is a very soft mineral with a hardness of 2 and will always be exposed at the surface when the rock is broken, carved or scratched because stones tend to fracture at the location of the weakest mineral. Comparative weathering studies performed on a core sample taken from the back of the stone, and a chip sample obtained from the split side, concluded that all the mica minerals had weathered away from the original inscription. So this again raised the question: how long would it have taken for this complete mica breakdown to have happened in a similar environment, and can that be used to date the rune stone?
A relative-age weathering study performed on chip samples collected (with permission) from biotite-rich slate tombstones from a cemetery in Hallowell, Maine. This area has a very similar climate and weathering pattern as Kensington. The mica minerals had began to come off the surface on the carved surfaces of the tombstones, primarily from the mechanical processes of wetting and drying, and freeze-thaw cycling, after about 200 years. But the mica breakdown was far more advanced on the KRS carved surfaces. Therefore, because all the micas are gone from the original inscription of the Kensington stone, it must date to more than 200 years from 1898, when it was pulled from the ground, because it hasn’t been in a weathering environment since.
Summary of Geological Findings On The KRS
1. The Kensington Rune Stone is a 2 billion years old meta-greywacke indigenous to Minnesota.
2. The skilled stone carver intentionally split the larger glacially deposited slab into the final roughly 2:1 dimensional shape prior to carving the inscription.
3. The root leaching on the back of the stone is consistent with the first-hand witnesses’ testimony of the discovery.
4. The cleaning of the inscription with a nail by Olof Ohman has caused unwarranted confusion and bias by investigators over the past 112 years
5. The pyrite evidence is consistent with the original inscription being older than 26 years at the time it was discovered, and therefore not a hoax.
6. The mica tombstone study is consistent with the original inscription being older than 200 years from 1898, and therefore not a hoax
7. On geological evidence alone, the Kensington Rune Stone cannot be a late 19th Century hoax.
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