Acknowledgements

            Without the help and support of individual firms and people it would sometimes take much longer for news of new treatments and synthetic processes to reach members of the trade. The AIGS Identification, grading and Research Laboratory is grateful to members of the trade for making samples available for testing thus contributing to better understanding of new products and processes pertaining to the jewelry industry.

Moldavite

            The first recorded occurrence of moldavite was in 1787 in western Moravia, and around Ceske Budejovice (Budweis) near the Bohemian river Moldau (Webster, 1983) from which the name moldavite was derived. Since that time man has been fascinated with this bottle green material. Bangkok even has a shop which specializes in such natural glasses.

            Separating man-made glass from the natural glasses has always created problems for gem identification laboratories using conventional identification procedures. Recently a known sample of moldavite was supplied to the AIGS laboratory for study by Dr. Charles Arps of The National Museum of Natural History in The Netherlands.

            Moldavite is singly refractive and has a refractive index between 1.488 and 1.503, a specific gravity between 2.34 and 2.39, an absorption spectrum showing ill-defined bands in the blue and vague band in the orange, and has no reaction to either long wave or shortwave ultraviolet radiation.

            Under microscopic magnification a myriad of gas bubbles was observed along with the coarse swirl marks characteristic of this natural material (Figure 1).

            The elemental composition examined using Energy Dispersive X-Ray Fluorescence (EDXRF) (Figure2) shows a host of elements including magnesium, aluminum, silicon, potassium, calcium, titanium, manganese, iron, rubidium, strontium, and zirconium.

            Microscopic evidence combined with the observation of the elemental composition makes the separation of man-made glass and natural glass a much easier task.

Raman update

            Raman spectroscopy was introduced in this column in the June/July 1995 issue. Since that time work has continued to progress. The following are some of the spectra that have been collected for inclusions in gemstones.

            Diamond Recently a diamond was submitted to the laboratory to verify the nature of the color. Upon routine microscopic examination two octahedral crystal inclusions ware observed. The Raman spectrum proved these inclusions to be diamond (Figure3). This can occur because diamonds grow in stages as opposed to a continual growth process (Gubelin and Koivula, 1986).

            Uranium-Pyrochlore Finding a uranium-pyrochlore in a blue sapphire created some excitement in the laboratory because the Raman spectrum could be added to our growing data base (Figure4). Uranium-pyrochlore, a tantalum and uranium bearing mineral, has been used to determine that the origin of the blue sapphires in either Pailin, Cambodia or Australia (Gubelin and Koivula, 1986).

            Olivine The host crystal for the inclusion in Figure 5 is a diamond from the south of Thailand. The Raman spectrum reveals that the included crystal is olivine. Diamonds are a by-product in the tin mining industry which existed in the south of Thailand for many years.

            Unknown Many pieces of jadeite containing ill defined crystals through the AIGS laboratory. When a jadeite cabochon containing a well defined colorless crystal was submitted for testing the possibilities for identifying this included crystal were quite good. Figure 6 shows the crystal and it’s very clear Raman spectrum. Unfortunately this spectrum could not be matched in our data base or any other reference materials. The search goes on.