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<p>[QUOTE=&quot;Ed Zak, post: 19824, member: 824&quot;]I must add my two red cents...</p><p><br /></p><p>Copper is indeed a very reactive metal and rarely is it found in a state of &quot;red-orange&quot; luster.&nbsp; For instance, copper reacts easily with sulfur to form copper sulfate...which is dark in color.&nbsp; It is a problem here in Florida (shallow wells and springs are loaded with sulphur) because many cheap dentists use copper-loaded dental alloys (at the expense of gold) which initially look great, but a year later their patients return and ask why their &quot;gold&quot; crown turned black.&nbsp; Also, sulphur gases are present in the air we breathe so much that some areas smell like rotten eggs...thanks to sulphur.</p><p><br /></p><p>Copper also easily oxidizes which is also dark in color.</p><p><br /></p><p>Silver does not oxidize, it tarnishes. Metals that don&#039;t oxidize or tarnish are called Noble metals.&nbsp; Metals like gold, palladium and platinum are examples of Noble metals which neither tarnish nor oxidize.</p><p><br /></p><p>So...the chance of finding a copper below AU conditions with luster is 99.99% likely of cleaning and/or dipping.</p><p><br /></p><p>So much for the class on metalurgy.[/QUOTE]</p><p><br /></p>

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