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<p>[QUOTE=&quot;robinjojo, post: 4825473, member: 110226&quot;]I&#039;ve seen toned gold coins, mostly 8 escudos cobs.&nbsp; The toning, such as it is, tends to be reddish.&nbsp; I&#039;ve never seen blue before on a gold coin.&nbsp; If it was a silver coin, that color would be expected.</p><p><br /></p><p>Pure gold does not tone or tarnish.&nbsp; It is the alloy, usually copper, that can create the red hues.&nbsp; I&#039;ve also seen old US $20 coins from the 19th century with a greenish cast.&nbsp; Again, I think the copper used for the alloy causes this type of toning.</p><p><br /></p><p>The blue areas on the coin are unusual, I think.&nbsp; Perhaps they were caused by something that the coin came into contact with.&nbsp; Some old envelopes were high in sulfur, such as the manila paper envelopes, so that might be a cause.</p><p><br /></p><p>Another possibility is that the coin has silver as its alloy, instead of copper. If that is the case, then blue toning could occur.[/QUOTE]</p><p><br /></p>

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