The Society for Sedimentary Geology (SEPM) has announced a bizarre article in their journal PALAIOS that joins together ‘forensic’ palaeontology and archaeology in order to detect origins of the millstones frequently used in the 1800s. While all millstones were used similarly at the time, millstones quarried in France were substantially more highly valued that similar stones quarried in Ohio, USA.
Over four years the scientific team visited historical localities in Ohio to locate the millstones, they then proceeded to study and identify the unique characteristics between the desirable French buhr and the less desirable Ohio buhrstone. Both of these types of millstones were composed of an exceptionally hard rock call chert, and at a glance they look extremely similar. However, after a close examination the scientists were able to confirm that the French buhr was also comprised of fossils that originated from a freshwater environment, including algae and snail fossils. It was also concluded that the Ohio buhrstone was quarried from a considerably older rock unit. The Ohio rock unit, which is said to have likely been laid down in a Paleozoic marine environment, included invertebrate fossils such as fusulinids, pelmatazoans and brachiopods.
A key feature that was extremely useful for the millers was the porosity of the rock; where fossils left empty cavities. Oliver Evans, famous inventor and millwright, exclaimed in 1795 that pores, “larger in diameter than the length of a grain of wheat” were in fact not desirable. The authors suspect that the fossil assemblages from the Ohio buhrstone may have made these millstones less effective for milling, but this is a claim that requires further investigation.
Chert has been used for the manufacturing of tools throughout human history and the authors hope that these non-destructive techniques can be used to research the origins of other artifacts.
Contributing Source: American Geosciences Institute
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