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 Post subject: What does GDT stand for in gemmology?
PostPosted: Thu Jan 01, 2015 10:26 pm 
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I know this may be elementary for most of you. but its the first time for me! :cry:

Reading through old exam papers I found a reference to GDT.
What does it stand for please?


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 Post subject: Re: What does GDT stand for in gemmology?
PostPosted: Fri Jan 02, 2015 12:20 am 
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Can you please put this in context of how it was used?
Thanks.


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 Post subject: Re: What does GDT stand for in gemmology?
PostPosted: Fri Jan 02, 2015 12:52 am 
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Garnet Topped Doublet

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 Post subject: Re: What does GDT stand for in gemmology?
PostPosted: Fri Jan 02, 2015 7:47 am 
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Barbra Voltaire wrote:
Can you please put this in context of how it was used?
Thanks.


It's a badly posed exam question and I managed to transpose two letters.

Q : What is GTD?
Give 4 observations that would help you identify a GTD?
Why were they made?


I'm not sure its fair to use abbreviations in exams. This is the first time I have seen garnet topped doublets referred to in this way but I guess its in common usage.

Were they made initially to reduce costs? It seems like a lot of work unless there is financial gain. Were garnets rarer and more expensive in the past?

Thanks Barbara and Nathan


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 Post subject: Re: What does GDT stand for in gemmology?
PostPosted: Fri Jan 02, 2015 12:16 pm 
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Wikipedia has a nice page on doublets that contains the most important points.

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 Post subject: Re: What does GDT stand for in gemmology?
PostPosted: Fri Jan 02, 2015 3:37 pm 
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Gem 14 wrote:
Barbra Voltaire wrote:
Can you please put this in context of how it was used?
Thanks.


It's a badly posed exam question and I managed to transpose two letters.

Q : What is GTD?
Give 4 observations that would help you identify a GTD?
Why were they made?


I'm not sure its fair to use abbreviations in exams. This is the first time I have seen garnet topped doublets referred to in this way but I guess its in common usage.

Were they made initially to reduce costs? It seems like a lot of work unless there is financial gain. Were garnets rarer and more expensive in the past?

Thanks Barbara and Nathan


GTD is a silly synonym for a garnet and glass doublet. Im not a particular fan of "GTD" as it isnt terribly informative since the glass component is not described. They were made purely to act as a cheap simulant for expensive stones, namely Ruby, Emerald and Sapphire, while still providing some increased measure of abrasion resistance compared to glass alone.

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 Post subject: Re: What does GDT stand for in gemmology?
PostPosted: Fri Jan 02, 2015 5:02 pm 
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Nathan is right, GTD sometimes used as a trade name for any doublet (Natural, imitation, synthetic)

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 Post subject: Re: What does GDT stand for in gemmology?
PostPosted: Fri Jan 02, 2015 5:37 pm 
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How long has it been since garnet-topped doublets were even made? They're practically a historical footnote at this point--I can't imagine anyone this century talking about them so much that they needed an acronym. But maybe things are different in other sides of the trade...


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 Post subject: Re: What does GDT stand for in gemmology?
PostPosted: Fri Jan 02, 2015 9:03 pm 
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Scarodactyl wrote:
I can't imagine anyone this century talking about them so much that they needed an acronym.


I agree with you - I think we are heading towards language disaster with everyone over using acronyms! I never use them in exams and find them irritating in any context.

I went on a search for examples of doublets mainly at jewellery auctions and had no luck. I eventually got a nice example from a kind member on this forum for my collection.


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 Post subject: Re: What does GDT stand for in gemmology?
PostPosted: Fri Jan 02, 2015 9:15 pm 
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YAG, CZ, SG, RI, LWUV, SWUV, GIA, AGL, CIBJO, NAJA ?

I think there are several acronyms which are professionally appropriate....GTD threw me off, even though I see them with some frequency, I always call them garnet and glass doublets. :|


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 Post subject: Re: What does GDT stand for in gemmology?
PostPosted: Fri Jan 02, 2015 9:23 pm 
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Barbra Voltaire wrote:
YAG, CZ, SG, RI, LWUV, SWUV, GIA, AGL, CIBJO, NAJA ?

I think there are several acronyms which are professionally appropriate....GTD threw me off, even though I see them with some frequency, I always call them garnet and glass doublets. :|



I sometimes wonder if some examiners are purposely trying to trip students instead of testing depth of knowledge in gemmology.


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 Post subject: Re: What does GDT stand for in gemmology?
PostPosted: Mon Nov 20, 2017 7:57 am 
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GDT Stand for Garnet Topped Doublet...


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 Post subject: Re: What does GDT stand for in gemmology?
PostPosted: Tue Nov 21, 2017 12:47 pm 
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I'm with Stephen Challenor on this one, it must be 50 years since I saw a doublet of any description, and even then it had been picked out of some old jewellery.


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 Post subject: Re: What does GDT stand for in gemmology?
PostPosted: Tue Nov 21, 2017 12:48 pm 
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Sorry, Challener!


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