Is there such a thing as copper eating worms? 1817 large cent

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How on Earth would they do that? Surely there's almost nothing easier to notice and correct on a mold than a big, prominent, raised line.

 

If we take this into account plus a person with lots of spare time on their hands, I don't think this coin should surprise us. Any ideas as to the cause are just speculation, because just like stupidity, the possibilities are endless.

 

I don't have any photos of the coins I treated as I threw them away. I still have a bunch I need to go through and I will post some photos if I find another one with cracked shellac or varnish. The coins I treated had original surfaces after I removed the sealer with acetone, but the coins with verdigris had recessed areas where the verdigris had been removed down to the metal. The coin above could have had cracked sealer and just treated in acid, which would have penetrated the cracks and began to eat away at the metal before the remaining sealer was eaten away because the entire surface looks to have been impacted.

 

I'd say genuine, N-6 R-1 with some form of environmental damage.

 

I received this coin today and it is a genuine large cent. Something has eaten into the surface but left other areas mostly untouched. As the lines reach the edges, it has the same pattern and continues on the reverse. This coin must have been well coated as some have suggested. I do not see any signs of that material remaining. Thanks to everyone for their input. I will put this coin into my show and tell collection.

 

Maybe it could be due to impurities in the original planchet. If the smelting of the ore was incomplete and impurities were left in the copper it could have shown up in the planchets. In many metals, impurities tend migrate towards the grain boundaries when cooled (although I have no idea what happens in copper). These regions of higher impurities could have reacted faster with whatever caused the environmental damage on the rest of the coin.

It might be a stretch, but the metallurgy makes sense. The selective corrosion theory through cracked shellac that was previously mentioned is also a possibility.

 

Those don't look like any grain boundaries I've ever seen, and you'd need to work really hard to get monocrystalline zones that large.

 

Yeah, you wouldn't expect grains to be that large. But what if the impurities had high immiscibility or a lower eutectic than the copper. It could behave as a second phase that got stuck as the copper domains solidified.

Still a stretch but nothing else makes a lot of sense.

 

More of a stretch than that, I think -- I don't believe these planchets were annealed for the weeks it would probably take to grow zones that large.

I don't think we see a lot of other evidence for giant grain boundaries in early copper, but we certainly see plenty of evidence for (a) protective coatings applied to them, (b) cracks in such protective coatings that follow this same sort of pattern, and (c) environmental agents that attack unprotected copper surfaces.

But, again, I'm no metallurgist.

 

Looking closely at lady liberty, the entire portrait has been etched by environmental damage. That would lead me to believe this is PMD most likely from being coated by an unknown substance.