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<p>[QUOTE=&quot;Coinchemistry 2012, post: 2039274, member: 28107&quot;]I don&#039;t disagree with your chemistry argument, but I do disagree with your conclusion that gold cannot tone naturally over time.&nbsp; Your argument appears to be predicated upon the flawed assumption that the alloy is always homogeneous, but we know that this is not always the case.&nbsp; After all, if it was, we wouldn&#039;t have copper spots on gold coins.&nbsp; And when impurities such as the trace metals and copper mentioned previously accumulate in larger amounts near the surface, it is absolutely reasonable to believe that toning could occur via natural mechanisms although admittedly it would be a scarce occurrence (as it appears to be).&nbsp; And of the Saints posted in this thread and that I have seen on other coins, the color pattern and progression is very similar.</p><p><br /></p><p>Edited:&nbsp; And I could have been clearer in my comments about trace metals and the color of gold.&nbsp; While gold takes on a characteristic color overall based on trace metals of some branch mint dated coins for instance, the thrust of my argument was that improper mixing of the alloy with these trace metals (and as always the approximately 10% copper composition for this and other pieces) could accumulate near the surfaces and facilitate toning.&nbsp; I am not conflating overall color of the alloy as struck and toning over time.[/QUOTE]</p><p><br /></p>

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