| Summary: | <p>A refined methodology using light stable isotopes in precipitation to determine the formation location of copper minerals is tested, for the eventual use on archaeological bronzes that corroded in the soil environment. To do this, δ<sup>18</sup>O in historic brochantite and archaeological malachite is used to determine whether the region in which these common minerals formed may be identified when the δ<sup>18</sup>O is a function of the δ<sup>18</sup>O in meteoric water and temperature. The waters in each phase of the hydrologic cycle have distinct isotopic compositions and can yield information on climate or water provenance. The possibility that this δ<sup>18</sup>O study can be supplemented by including the hydroxyl-δ<sup>2</sup>H in brochantite or δ<sup>13</sup>C in malachite is explored as sub-studies.</p>
<p>This study shows no significant difference between the δ<sup>18</sup>O<sub>SO4</sub> in brochantite, and the δ<sup>18</sup>O<sub>SO4</sub> variances are about equal among the cities considered. Furthermore, there is no statistically significant correlation between δ<sup>18</sup>O<sub>SO4</sub> or hydroxyl-2H and the δ<sup>18</sup>O in precipitation, precipitation amount, pH, surface temperature, latitude, or age of deposit. About 50% of brochantite’s δ<sup>18</sup>O<sub>SO4</sub> is sourced from local meteoric water. Of the three SO<sub>2</sub> → SO<sub>4</sub> pathways that contribute oxygen in brochantite, oxygen percentages can be calculated for two pathways at a time.</p>
<p>The malachite data shows significant difference between the geographic groups surveyed, but does not suggest a statistically significant relationship between the δ<sup>18</sup>O or δ<sup>13</sup>C in malachite and the δ<sup>18</sup>O in local precipitation or surface temperature. A significant relationship is apparent between δ<sup>18</sup>O and δ<sup>13</sup>C with some clustering within sample sites. Therefore, a comprehensive study into the δ<sup>13</sup>C of malachite would be worthwhile. Climate-focused research also shows potential.</p>
<p>This work can be used to advise on authenticity issues or guide in provenance studies when choosing between suspected sites. Further refinement is necessary before it may be adopted for cases without suspected formation sites.</p>
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