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<p>[QUOTE=&quot;mithril21, post: 3468359, member: 102153&quot;]The <a href="https://www.fischer-technology.com/fileadmin/documents/tds/EN/TDS_XAN250-252_952-092_en.pdf" target="_blank" class="externalLink ProxyLink" data-proxy-href="https://www.fischer-technology.com/fileadmin/documents/tds/EN/TDS_XAN250-252_952-092_en.pdf" rel="nofollow">Fischerscope X-ray Xan 250</a> is a benchtop XRF instrument, not a handheld XRF. This is considered quantitative and highly accurate because each element is calibrated to standards. SEM/EDS is non-standard based and considered “semi-quantitative.” However, for this particular application, SEM/EDS is the superior method because of the size of the foreign metal.</p><p><br /></p><p>The element range on the XRF is Al - U, so it cannot detect the oxygen on the surface from over 100 years of oxidation. The oxidation changes the surface chemistry of the coin. One reason why the copper is less than 95%. EDS can detect oxygen, although it is not highly accurate. </p><p><br /></p><p>The smallest measurement spot size on this XRF unit is 0.3 mm diameter, depending on the measuring distance and the aperture. However, the spot size is typically closer to 3-5 mm diameter for these instruments using the standard size aperture. This is larger than the size of the foreign metal, so you are getting both chemistries combined into one which is then weighted to 100%. Another reason why it shows copper is less than 95%. EDS can have a spot size down to just a few microns. </p><p><br /></p><p>The analysis does indicate the presence of gold, so I do not doubt the foreign metal contains gold.</p><p><br /></p><p>If you live near southern Indiana, then I may be able to perform the SEM/EDS analysis for you if you want.[/QUOTE]</p><p><br /></p>

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