David Bright - Gemology

Petter introduced the speaker Mr. David Bright, who, after his studies in chemistry is currently working as an inspector at OPCW. David has the passion of gemmology and is now an accredited gemmologist after having obtained a diploma from the Asian Institute of Gemmological Sciences in Bangkok. His passion has led him to travel around the world and David has published several papers in specialised reviews.

David starts his talk by stating that his biggest interest in gemmology, which he defines as a forensic science, lies in the scientific aspect but he also deals with the commercial aspects of gems. The speaker then went on by saying that the main objective of gemmology is to be able to identify a gemstone, a mineral or a carving and to retrace its "history".

In order to achieve this goal the gemmologist has a series of analytical tools that range from very simple (magnifiers, polarisers and optical microscopes) to extremely powerful but expensive (FTIR, raman spectroscopy or laser ablated ICP-MS).

He then went on to explain that there are generally two types of gemstones which a gemmologist can sort: natural or synthetic, where, for instance diamonds or rubies, are obtained by a series of techniques like chemical vapour depositions, flux growth, flame fusion or hydrothermal processes.

A gemmologist will also be able to determine whether the gems (both natural and synthetic) have undergone physical or chemical treatments in order to enhance their properties and aspect. Among those treatments David cited the high temperature/high pressure treatments for diamonds or diffusion heat treatments, impregnation or fracture filling with high refractive index glass for rubies.

He then gave, thanks to some nice slides, examples of how the different analysis techniques work in the sorting of natural and synthetic rubies.

Finally he reminded the attendance that the gemstone market is a complicated one and that before buying a gemstone we should always ask the jeweller to certify the history of the stone.

The presentation was very appreciated, especially by our male members, who now have a good excuse not to buy gemstones by fear of being tricked and David kindly answered some questions. Giuseppe expressed, on behalf of the Club, a vote of thanks and Julia presented the speaker with a copy of our cookbook "Taste for life" as a token of our appreciation.

Here are some web pages from the speaker: http://gemwanderings.googlepages.com/ , http://gemwow.com/

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