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Discoloration on Heraclius gold solidus - what can it be?
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<p>[QUOTE="IdesOfMarch01, post: 3210469, member: 39084"]Elemental gold is inert and will not easily form ions that combine with other elements to form this discoloration. Gold <i>can</i> be dissolved in <i>aqua regia</i> -- a mixture of nitric and hydrochloric acids -- but this is unlikely to have happened just sitting in soil.</p><p><br /></p><p>There are two more likely reasons that a gold coin is discolored:</p><p><br /></p><p>(1) If the coin was not 100% pure, elemental gold, the non-gold elements on the coin's surface might have oxidized or combined with other elements in the soil to form this toning.</p><p><br /></p><p>(2) During the striking process, some iron from the die was transferred and imbedded into the surface and this iron has rusted to create the toning.</p><p><br /></p><p>I believe it's also possible that really difficult-to-remove encrustations have formed on the coin's surface, but this doesn't appear to have happened on this coin.[/QUOTE]</p><p><br /></p>
[QUOTE="IdesOfMarch01, post: 3210469, member: 39084"]Elemental gold is inert and will not easily form ions that combine with other elements to form this discoloration. Gold [I]can[/I] be dissolved in [I]aqua regia[/I] -- a mixture of nitric and hydrochloric acids -- but this is unlikely to have happened just sitting in soil. There are two more likely reasons that a gold coin is discolored: (1) If the coin was not 100% pure, elemental gold, the non-gold elements on the coin's surface might have oxidized or combined with other elements in the soil to form this toning. (2) During the striking process, some iron from the die was transferred and imbedded into the surface and this iron has rusted to create the toning. I believe it's also possible that really difficult-to-remove encrustations have formed on the coin's surface, but this doesn't appear to have happened on this coin.[/QUOTE]
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Discoloration on Heraclius gold solidus - what can it be?
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