Not an error, it has been subjected to heat causing the clad layer to separate and bubble.
I think that I will keep it in my blemish collection...It is the first time I have ever seen anything like it...lolIt's damage. Worth 25 cents.

Does anyone know if hemimorphite specimens are worth anything...I came across a little deposit in Mexico that has some really nice specimens of said mineral...I was just curious IF they might be worth more than the quarter for your thoughts I posted in this thread
Ed T