In this case study, Beryllium concentrations (in ppm Wt.-%)are ten times lower than the Mg-concentrations (Table 4) and thus their direct contribution to the color is questionable and needs further research (Compare also Lit. 29 and Internet Ref. 11). The yellow or orange color is formed at Mg/Ti greater than one, and at relatively lower Cr-concentrations (Fig. 41, 57, 61). The orange color is also formed outside the zone containing Beryllium (See Fig. 57). The presence of Ti above 150ppm hampered the formation of these orange color centers (Fig. 57). The nature of these orange color centers are interpreted as trapped-hole type (See Lit. 04). Orangy-pink colors "Padparadscha" are formed in the presence of different color causes, such as Fe³⁺-pairs, Cr³⁺, Mg²⁺- trapped-hole color centers, and at Ti-concentrations below a critical level (Fig. 26, 27, 28, and 29).

6.) The concentrations of Mg and Be are directly correlated in the treated part of the gemstone. As increasing Be-concentrations correlate with decreasing Mg-concentrations (Fig. 50, Fig. 57 and Fig. 62), this suggests Be replaces Mg positions in the corundum lattice. Profile studies show that the migration of Mg towards the core occurred (e.g. Fig. 50 and Fig. 62), however other elements - such as Ti - also migrate. Ti-migration is best seen when related to pre-existing whitish rutile dust bands (Fig. 57), or around Ti-oxide minerals (Fig. 68). A very distinct blue halo is formed (Fig. 68), interpreted as color from Fe²⁺-Ti⁴⁺ pairs (Ti from migration and Fe from the sapphire’s composition) (Fig. 57).

The color in the enhanced sapphire depends on the chemical differences in the parent sapphire material, while the presence of Ti is found to be the most critical element in preventing the treatment's success (See Fig. 41 and 57). Color zoning is related to the reaction zone of the treatment and can be either confined to the rim or found within the gemstone, depending on the extent of the treatment and the gemstone's chemical composition (See Table 7b,c). The use of a high temperature is indicated by the surface melting of the sapphires (Fig. 14 and 15).

Such treatment conditions - including diffusion of elements into the surface, change of oxidation state of Fe, and formation of color centers - can be achieved during heating at a very high temperature near the sapphire's melting point under oxidation conditions (See Lit. 04).
The migration of cations towards the center of the gemstones may be related to Be-diffusion in the heating runs (Fig. 8, See Internet Ref. 11).

Identification Test

The identification of this material can be based on gemological tests, including the use of a microscope (Internet Ref 01, 03, 04 and Fig. 68), particularly in differentiating against diffusion-treated gemstones. Use of special methods - including the detection of Beryllium - are extremely difficult and costly. It uses SIMS (Internet Ref. 07), or LA-ICP-MS (this work). These instruments are commonly unavailable for routine testing. In addition to the Internet published test, the additional UV-Experiment can be of help (Table 1, Fig. 4 and Fig. 6). This test cannot be used to differentiate against irradiated gemstones or unheated gemstones, but can help to differentiate against other heated gemstones (group E).

Consequences for New Product Disclosure

The enhancement process producing these colors by internal migration seems to be related to diffused elements from outside sources (Internet Ref. 05, 09, 11, Lit. 18).

We agree with GIA's On-line publication on the Internet when they state that the results of their investigation strongly suggests that Beryllium is not the direct cause of the surface-related orange color layers and that it is possible that the diffusion of Beryllium and perhaps other elements into the stone may be creating a reaction with the inherent chemistry in the corundum that gives rise to the yellow to orange coloration (Internet Ref. 11).
Diffusion of light elements (e.g. hydrogen, deuterium etc.) into gemstones in course of the heat enhancement process is not a new aspect (Lit. 05). As long as the elements involved in the treatment are not directly causing the color, these type of treatments were traditionally considered gemstone enhancements (E) and were not classified as "diffusion treated" (T). The new enhancement must not be classified as surface diffusion-treated (See Internet Ref. 03) - the term 'treated' (Internet No. 08) or 'bulk diffusion' (Internet Ref. 12) may be more appropriate. The word 'diffusion' is commonly understood in the trade as coloring by introducing trace elements (Fe, Cr or Ti) from outside into the gemstone's surface Lit. 16), and thus it is suggested not to disclose the new treatment with a phrase including the word 'diffusion' (See example Internet Ref. 12 or Internet Ref. 03). To recognize these facts the disclosure of the gemstones in the enhanced category can be proposed as following:

Enhanced (E) by heat and diffusion inducing color zoning by internal (I) migration (M) of trace elements and defects, and formation of color centers

Or in short: H(Be)*
* H(Be) is a registered Trademark of GRS (modified on 2003)
Gemresearch Swisslab AG, Lucerne, Switzerland.