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<p>[QUOTE=&quot;GDJMSP, post: 984567, member: 112&quot;]Jim, you don&#039;t need any subscription to read this - <a href="http://matsci.uah.edu/courseware/mts501/reports/sschwitalla.html" target="_blank" class="externalLink ProxyLink" data-proxy-href="http://matsci.uah.edu/courseware/mts501/reports/sschwitalla.html" rel="nofollow">http://matsci.uah.edu/courseware/mts501/reports/sschwitalla.html</a></p><p><br /></p><p>And in it they say what I quoted below - </p><p><br /></p><p><i>&quot;Of all the metals, gold, chemical symbol Au, has the lowest tendency to react with air to form oxides.&quot;</i></p><p><br /></p><p>Now that does not say that gold cannot or does not react with air to form oxides, it merely says gold has the lowest tendency&nbsp; of the metals to do so. That tells me that gold <b>can</b> form oxides due to exposure to air.</p><p><br /></p><p>And they say - </p><p><br /></p><p><i>&quot;Structurally, <u>Au2O3, the most stable Au oxide,</u> exists as a square planar compound, exhibiting distorted octahedral geometry coordination on the Au3+ ion and a tetrahedral coordination on the O2- ion. The distorted geometry occurs as a result of d8 orbital splotting, the Jahn-Teller effect. Additionally, radius ratio rules support a distorted octahedral geometry by predicting an octahedral coordination for Au3+ (r = 0.85 A) and a tetrahedral coordination for O2- (r = 1.32 A). [3,5,7] <u>Despite its observed geometry, Au2O3 and other AuxOy compounds exist in an amorphous state.&quot;</u></i></p><p><br /></p><p>Now an amorphous state merely means that the oxide does not have a crystaline structure.</p><p><br /></p><p>definition of amorphus in relation to&nbsp; - </p><p><br /></p><p>3. Petrography,&nbsp; Mineralogy . occurring in a mass, as without stratification or crystalline structure. </p><p>4. Chemistry . not crystalline. </p><p><br /></p><p><br /></p><p><br /></p><p><i>&quot;One hypothesis that could be made for lower pressure / lower temperature reactions is that the positive slope of the near verticle phase boundary for the stability of the Au metal would decrease to the point that the area of stability of the Au metal would be dominant. <u>By regraphing the data on a ln PO2 vs T plot, a linear relationship would probably be seen with the Au metal area of stability located at the <b>pressure and temperature ranges existing in nature.&quot;[/</b></u> </i></p><p><br /></p><p>Now that is also pretty plain. Gold can tone (form oxides) due to conditions existing in nature. I don&#039;t know how it could be said much plainer than that.</p><p><br /></p><p>But perhaps the most interesting thing of all that the study indicates is this - </p><p><br /></p><p><i>&quot;A review of the literature indicated a scarcity of research on the reactivity of Au with oxygen.&quot;</i> </p><p><br /></p><p>Now again, I submit that the reason there is a scarcity of research on the subject of gold toning (reactivity of Au with oxygen) is because people have bene told all their lives that it doesn&#039;t happen. So nobody bothers to find if that is true or not. They just accept it as being true.</p><p><br /></p><p>But actual research seems to prove that it is not true.[/QUOTE]</p><p><br /></p>

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