Identification of microinclusions in the nanometer dimension by electron microprobe analysis. The chromonophores of colored sunstones.

Valid identification of microinclusions, which is essential to understanding the genesis of minerals, can require more than traditional petrology that is focused on their chemical compositions. By combining determination of chemical composition with X-ray characteristic imagery of atoms, electron microprobe analysis of individual microinclusions provides a means by which to identify their chemical structures or mineral species. Here we apply this technique to identification of microinclusions and show the results obtained substantiate the origins of colors for sunstones: A transparent red-color of the Oregon sunstone is due to the distribution of mixtures of both native coppers and cuprites in oval-shaped thin films, while the transparent-green type is due to the distribution of their similar mixtures in short microcolumns.