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<p>[QUOTE=&quot;desertgem, post: 863527, member: 15199&quot;]The main difference in the desert patina seems to be&nbsp; the presence of a comparatively high concentration of Silicon along with Chloride in a very dry environment for hundreds or thousands of years. The blues and greens ( verdigris) seem to start out similar to modern ( 200 years or so) copper/silver types of coins, but over the extended time period, layers of different composition patina develops over the original. But as with many subjects of antiquity, there are different theories.</p><p><br /></p><p>Bad Thad has done a lot of research on modern verdigris composition for his upcoming book, and maybe he will expand into ancients also.</p><p><br /></p><p>Jim[/QUOTE]</p><p><br /></p>

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