X-Ray Absorption Spectroscopic Study of Copper in an Amorphous Copper-Silicate: Chrysocolla

XANES and EXAFS data indicate that chrysocolla does not contain domains of Cu-metal or Cu-oxides as previously hypothesized, but is most similar to dioptase, a chemically homogeneous crystalline Cu-silicate. The first shell around Cu in chrysocolla is similar to that in dioptase, indicating Cu is coordinated by four oxygens. However, the second shell around Cu in chrysocolla is significantly different than the second shell surrounding Cu in dioptase. The larger amplitude second shell for chrysocolla compared with dioptase is found to be primarily due to differences in the Cu-Cu environments between these two materials.