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<p>[QUOTE=&quot;desertgem, post: 1345734, member: 15199&quot;]Rainbow appearance occurs whenever there is thin film interference, and this may be from a ultrathin layer of silver sulfide (toning), or an oil, or other chemical compound put on the surface. That it was removed by the acetone is a very strong indication that the original coloration may have been artificially produced by an oil or organic, as acetone won&#039;t remove an inorganic layer. Others may differ, but I approve of the action and the result. <img src="styles/default/xenforo/clear.png" class="mceSmilieSprite mceSmilie1" alt=":)" unselectable="on" unselectable="on" />[/QUOTE]</p><p><br /></p>

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