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<p>[QUOTE=&quot;qwasty, post: 986405, member: 27130&quot;]Things can be made absolutely pure, but they must be protected. For example, silicon technology can produce pure silicon crystals, but upon exposure to the atmosphere, the silicon begins reacting with the atmosphere. Same goes for the international kilogram.</p><p><br /></p><p>Gold is made commercially pure by using electroplating. It still isn&#039;t EXACTLY completely pure, but it&#039;s close enough that you won&#039;t see any funny spots developing on it. </p><p><br /></p><p>As others have pointed out, 1.000 gold is not pure. Look up &quot;significant figures&quot; to see why. The ultra short version is that .9999 gold is actually something like .99985, with the last nine being the result of rounding. To call something 1.000 gold is technically correct, but it only means that it&#039;s pure out to 4 significant figures. In other words, &quot;1.000&quot; means the same thing as &quot;.9999&quot;.</p><p><br /></p><p>Also, there are other ways of discoloring a metal besides a chemical &quot;toning&quot; reaction. The metal surface can adsorb (stuck on the surface) or absorb (soaked deep in side) other substances. Hydrogen gets into pretty much everything. However, adsorption and absorption usually do not make spots. Instead, they make a consistent, even change of some sort. Usually it&#039;s not visible as a color change, but instead it changes the hardness or, malleability, or ductility of a metal - or something like that.</p><p><br /></p><p>I suspect most of the gold &quot;toning&quot; we can see with our bare eyes is actually just microscopic dirt adhered (adsorbed?) to the surface, which then gets old and &quot;tones&quot;. I doubt that any of the natural atmospheric chemical reactions that gold is capable of would occur often enough for it to be visually apparent. If it were, you&#039;d probably have to be more worried about the atmosphere dissolving your lungs.</p><p><br /></p><p>The impurities in &quot;pure&quot; gold, however few they may be, may be concentrated in &quot;spots&quot; where JUST IN THAT SPOT, the purity of the gold might be only .5000. Overall, the gold is .9999, but in JUST ONE SPOT, there&#039;s a bit of something else. That&#039;s how you get spots in &quot;pure&quot; materials.</p><p><br /></p><p>Unless the ancients used electroplating methods, they probably could not achieve equivalent methods of purity. It is actually possible that the ancients may have experimented with electroplating. Look up the Baghdad battery for an archeaological find of ancient electric battery technology sufficient for gold electroplating. If electroplating was done, it was very uncommon, which is why only one ancient battery has been discovered, as far as I know.</p><p><br /></p><p>Spots should be no surprise to anyone, no matter how pure the gold is, if it&#039;s not kept in a vacuum chamber. The world is full of crap that can get into the gold while, or even after it&#039;s minted. It doesn&#039;t take much to make a colored spot. The residue from a fingerprint is far more than enough to do that, and nobody would argue that the fingerprint changes the purity of a gold coin. The impurities that give you spots on modern coins are in much smaller quantities than what comes from a fingerprint, just to give you some perspective.[/QUOTE]</p><p><br /></p>

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