The Gilfoil Copper --- Exciting XRF Analysis!
Some months ago I posted photos and details on an unknown copper which I suspect is an example of the "halfpence" struck by Private William Gilfoil at Fort Crown Point in the Colony of New York circa 1770. These coins were, according to British Court transcripts, "beat out to the size of halfpence" and passed current at Fort Crown Point at 14 to the shilling. Gilfoil made these from the copper hoops from Gunpowder barrels, which were stamped with the British Broad Artow near the rivet which joined the hoop ends. Recovered pieces from neighboring forts show this stamp well formed with the central shaft showing tapering to a point before reaching the top of the arrow, exactly the same as the imprint on my coin. While no coins exactly like mine have been discovered, a very similar farthing size piece has been recovered with "a row of parallel dents coming in from one side". Also, two segments of Spanish 2 Real coins have been recovered counterstamped with a very small British Broad Arrow. These characteristics tie all four pieces into a common theme. ------- I have had my coin analyzed to determine its metallic composition and the results are very exciting. Here is the analysis: Cu 94.8 Zn 1.03 Ag 0.38 Sb 0.52 Fe 0.09 As 0.20 Pb 1.82 Bi 0,87 (Cb Sn Au not present). The alloy and trace elements are VERY significant . The trace elements of silver and arsenic, along with the absence of nickel tie this copper to the Great Copper Mine of Parys Mountain in Wales , known as Anglessey Copper. The deposit was so large the Royal Navy was able to sheath its ship hulls to protect them from ship worms. The copper was rolled out to thin sheets. After getting the opinion of a metallurgist, the alloy proves to be purpose made. Lead, Zinc and Bismuth do not occur at this level as traces from refining, but were added on purpose. This alloy would have exceptional malleability as well as corrosion resistance.... Exactly the features needed to roll out this metal thin, allow it to be formed into hoops and resist corrosion during sea journeys or long storage. Very important also is that the Parys Mountain deposit was mined from 1768 to 1800, when it was nearly totally mined out. ----- So, we are getting closer and closer to Authentication! The work that remains to be done is a field trip to Peebles Island NY where thousands of recovered artifacts are stored. Matching the metal to hoop fragments found on site, examining the "farthing" and it's dents and hopefully XRF testing will follow, which if found to be of a matching metal.....these are a few more things needed before conclusive decisions can be made in order to get the Gilfoil Copper recognized and given its proper place in Colonial Numismatics. .