Jump to content

'glg' Or 'gem-A' Certificate????


Recommended Posts

I bought a diamond ring today on the famous Hatton Garden street in London.


But it is certified by The Gem Testing Laboratory of Great Britain, which I don't think famous at all. (The seller told me the certification is called 'GLG' and he admitted that it is very rare.)


I googled the laboratory but it is associated with the British gem association 'Gem-A' but the lab closed down a few years ago.


Has anybody heard of this 'GLG' certification issued by the Gem Testing Laboratory of Great Britain?


My ring was graded as 'D' for colour and 'VS1' for clarity. But I am so concerned whether it is reliable. 


The seller told me they can exchange the diamond with 300 British Pounds for GIA certified diamond. But my ring has such an unusual emerald cut and I don't think I can find the exactly same cut for another stone.


Would you recommend me to exchange with the GIA certified diamond? Or should I ship to GIA to get certification of the current diamond? What do you think of the reputation of 'GLG' certificate?  I am concerned whether the actual grade can be assessed from the current 'D' to 'G' or it is not 100% diamond. 




Link to comment
Share on other sites

GTG was a fine lab, and Gem-A is a fine outfit.  Not that this answers your question.  That has to do with what you're trying to accomplish.  Any competent gemologist can tell you if it's a diamond and if it matches the GTG document.  I presume the selling jeweler already did this if it's a recent purchase.  Second guessing the lab is an entirely different sort of question.  Are you trying to sell this?  Is this for insurance?  Curiosity?  Are you otherwise unhappy with it?  Are you just worried that the seller might be misrepresenting something?


Imagine we were talking about a purebred dog.   The paperwork has nothing to do with whether or not it's a fine dog or even if there's an issue with the genealogy.   Presence of papers in no way makes the dog any better.  When it comes into play is when you're buying or selling it.  The purebred costs $1000 and a perfectly good mutt is free.  THAT'S about the paperwork, and yes it matters who issued it.  Is the purebred worth more?  Yes.  Sellers ask more, and they get it.  Buyers knowingly pay a premium and are pleased with the results.  That's not such a bad definition of added value.  Is it 'better'?  No, at least not in the usual ways that one dog is better than another. 


Are GIA graded diamonds better?  No.  It's a rock.  GTC didn't make it and neither did GIA.  What GIA is doing is supplying a pedigree.  They're well regarded for consistency and accuracy.   That's why people like them. They are, by far, the best regarded lab in the world.  Their service costs a hundred dollars or so but it's a bit of a chore to submit stones from the UK.  As I recall, Gem-A set up a take in window in London to submit stones in bulk when they shut down the GTG but I'm not exactly sure how the logistics work.  I would imagine your jeweler does.  Is it worth submitting?  That's up to you and goes to the questions above about your objectives.  One warning.  Be prepared for it to take months. 

Edited by denverappraiser
  • Like 1
Link to comment
Share on other sites

Denverappraiser, thank you very much for your kind explanation!  :lol:


I do not have any intention to sell this ring, but I just want to make sure that I was not scammed.


The seller told me that the grade for diamond color and clarity can go down by one grade if GIA assesses it. 

Can you please let me know how many grades usually go lower if GIA assess the diamond certified by other organisations?

I paid 3,000 US dollar for a ring with 0.54 carat with D, VS1, and good cut. but I am just concerned that I paid too much for actually a lot lower quality diamond..That was the reason that I wanted to get GIA assessed it. but as you said, shipping and insurance cost is definitely too much. I had alternative option for GIA certified diamond with F, VS1 with 2,700 US dollar.  


I also have another question. 

I chose my ring because it is a lot more sparkly than other emerald cut diamonds. 

Just curious what can make the emerald cut diamond far more sparkly than others? 


Thanks in advance! 

Link to comment
Share on other sites

There is not a conversion chart between labs.  Sorry.  The problem is one of consistency.  If I were to say, for example, that clarity grades are usually within 0-3 grades, what have you learned about YOUR stone?  Nothing.  It might be dead on, it might be way way off.  The same applies to color.  If you want to know what GIA would say, either have it graded by a gemologist you trust to estimate what they think GIA will say or send it to GIA and get it straight from the proverbial horse's mouth.  What your jeweler is telling you is that THEY trust GTG and possibly their own in-house grading.  How much weight you put on this boils down to your assessment of the jeweler more than of the stone.  


'Sparkle' is a function of cutting.  Some are better than others.  Neither color nor clarity have much to do with it beyond a question of general transparency, something that won't be an issue if your VS1 is anything like accurate.  I've seen neither your stone nor the ones you're comparing it to.  I couldn't even begin to answer what the differences are. 


$3000 is a bit pricey for a 0.54/D/VS1/EC but it is going to depend on the ring.  Some cost a lot more than others.  It's also worth noting that UK has import taxes that apply here and fancy stores in Hatton Garden aren't the cheap way to buy things anyway.  You surely already knew that.  Whether or not they're worth their cost is up to you but yes, you could probably get something similar for less elsewhere.  

Edited by denverappraiser
Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Create New...