Chemical Composition

X-ray fluorescence analysis reveals an average composition of that part of the ruby that was exposed to the X-ray beam, such as part of the table of a faceted stone. It has shown that the rubies contain significant trace-element concentrations of Cr (chromium), Fe (iron), Ti (titanium), V (vanadium), and Ga (gallium) (see the Table).

A reasonable correlation was found between R.I.'s and chromium concentrations, and a good coincidence was obtained in a plot with the sum of trace-element concentrations.

Refractive indices were correlated with chemical composition in the eight Mong Hsu rubies analyzed by X-ray fluorescence for which refractive indices could be measured. A distinct increase in refractive indices is caused by increasing trace-element contents.

The trace-element patterns of Mong Hsu rubies are useful to distinguish faceted samples from their synthetic counterparts. Although there may be some overlaps with other natural rubies originating from marble deposits, trace-element contents of individual samples can also be helpful for locality determination.