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 Post subject: New Tables of Gemstone Identification
PostPosted: Tue Jul 27, 2021 6:57 pm 
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I just received the latest (2021) version of New Tables of Gemstone Identification, by Roger Dedeyne, Gerald Gay and Agnes Mainguy. I have used the original Tables of Identification almost on a daily basis since it was originally printed in 2007.

The text is somewhat similar to the one written by Birgit Gunther in 1981, which was a required textbook at DGemG when I was a student there. I purchased the original Dedeyne book because my original German text was out of date, out of print and falling apart.
Brilliant move on my part because the Tables of Gemstone Identification was a major upgrade.

The updated version has the same format as the original but with several new additions reflecting the change in our industry and the gemstones currently available on the market.

It enables one to positively identify an unknown, using standard gemological instruments, with a series of eliminations after each optical test.
This book contains the most up-to-date tables for the identification of gemstones. A must for every gemmologist.

Chapters are as follows:

Table 1. Stones are listed with increasing refractive index, using the lowest refractive index value, indicated in red, as a reference. The extremely wide refractive index range of glass would result in a confusing and unnecessary repeating of this substance all through the list. The gemmologist should refer to "Table 6" for further identification.

Table 2. Stones are grouped following their most encountered colours and listed following increasing refractive index.

Table 3. Stones are situated in density groups, increasing with 0.01 density steps. Stones belonging to a particular density group, are listed following optic character and further following refractive index.

Table 4. Stones are listed in alphabetical order.

Table 5. Stones are listed in alphabetical order. Supplementary information (colour, chemical composition, hardness, crystal system, cleavage, lustre, origin, mineral group, magnetic susceptibility, ...) although not immediately related to the identification, provides a possible confirmation of an obtained result.

Table 6. Glass being the most encountered imitation material, its gemmological properties cover a wide range of values. The relationship between refractive index and density is shown in a graph. The other charts (glass-ceramics, garnet group, enstatite group, feldspath group and emerald) can be helpful for a fast identification.

Table 7. The garnet group represents several commercially important gemstones. Correct identification may be difficult but is usually possible with the right combination of refractive index, density, spectrum and colour.

Table 8. Diamond imitations with a refractive index above 1.81 are separated in optically isotropic and anisotropic groups and further listed with increasing density.

Table 9. Many stones are in the market sold with incorrect names. Sometimes it is very confusing for gemstone buyers. Table 9 listed more than 1300 incorrect names used in the gemstone market.

Table 10. Tips & tricks that can help for easier identification of some stones.


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 Post subject: Re: New Tables of Gemstone Identification
PostPosted: Tue Jul 27, 2021 8:01 pm 
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Thanks Barbra! Would be a nice addition of valuable info. Have a referral to where they can be purchased? I guess I can search it.

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 Post subject: Re: New Tables of Gemstone Identification
PostPosted: Tue Jul 27, 2021 8:35 pm 
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 Post subject: Re: New Tables of Gemstone Identification
PostPosted: Thu Jul 29, 2021 5:53 am 
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Barbra, if you keep on with these excellent recommendations, I shall have to buy a bigger house!!!


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