Natural Yellow Sapphires E(IM1)

Results LA-ICP-MS

The yellow sapphire was produced from a near colorless sapphire by the new treatment, cut in half, and then the chemical compositions were measured in a profile across the sample - see Table 6. Chemical zoning was found in the gemstone confined to the faceted surface of the sample as shown in Fig. 61 and 62. This zoning was therefore produced by the new treatment.
The dominant trace element in this gemstone is Fe, while all other elements found in the gemstone are below 200ppm. Beryllium concentrations are restricted to the gemstone’s outer zone (15 ppm maximum), the rim of the gemstone shows a depletion in Fe, and Fe and Mg is enriched towards the center. A large portion of the gemstone reaches levels higher than approx. 800ppm of Fe-, and Mg concentrations are always greater than Ti-concentrations. This seems to be the ideal combination for coloring the sample yellow by the new treatment (such as Mg²⁺-Trapped Hole Color Centers) (Lit. 4).
The gemstone’s outer rim - where Be concentrations are found - is the location of orange colored unstable color centers produced by UV light (See Table 1). These faded after mild exposure to heat.

Natural Unheated Purple Sapphires

Results LA-ICP-MS

This sample is representative for those that can be successfully heat treated with the new method (three samples analyzed in detail by LA-ICP-MS (details Table 6) and Fig. 23 (Field LP and P)). It emphasizes here that the same elements are found as is the case with the treated samples (Fe, Cr, Ti, V, Mg, Ga), except Be which is missing in the natural Fancy Sapphires. Of particular interest is the ratio of Mg/Ti which in this sample is equal to 1.
Note: The pronounced chemical zoning (observed in the treated samples) is absent.

Fig. 63 Microphotograph of a purple sapphire unenhanced by heat. LA-ICP MS craters are shown (80 micrometer diameter). Representative for samples that can be successfully heat treated with the new method.

Fig. 64 Profile across the sample of Fig. 63 shows the chemical variations (in ppm) in the gemstone due to its natural composition. No depletion and no symmetric chemical zonings were present, particularly regarding the lighter elements Mg and Ti. Note: Similar chemical compositions (dominantly Fe, Cr, Ti, V, Mg, Ga) are present as in the enhanced counterparts, with the exception of Beryllium which is absent. Ti concentrations are almost equal to Mg concentrations (Details see Appendix pages 46 and 47).