New Mineral Named After GIA’s John Koivula
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 Post subject: Re: gemval historical value?
PostPosted: Tue Jul 29, 2014 4:16 am 
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Congratulations for a very insightful post :D

I do own imperial topaz gems, all of which I bought in Brazil. The most expensive one comes from the most famous jewellery in Brazil and is certified hence registered with the seller which has set its own classification in terms of colour scale (yellow, orange, pink, salmon and sherry red) and tone (very light, light, medium, medium dark, dark, very dark). The cheaper stones came from a gem shop in Ouro Preto not far from one of the mines. In this case the stones are not classified for colour and tone; I paid a lot less for them. My certificate says that the salmon stones are heated to eliminate the yellow hue.

In general Cr gives a green colour to a gemstone, eg emerald as a variety of beryl. However the red in rubies (corundum variety) is supposedly also given by trivalent Cr, which replaces Al in both group of minerals.

It would need a very experienced gemmologist to determine that an orange-brownish topaz is an imperial one or comes from another locality.

The pricing gets tricky for most gemstones. In the end what in my opinion dictates the price within the upper end gemstones is their spark. This is clear to me when my wife wears her aquamarine from Brazil, which I bought again from the famous jeweller. Its spark is incredible, even better than that of the imperial topaz. Personally I would never spend the kind of money I gave to the Brazilian jeweller to an eBay or internet seller.

Going back to my original question about Geoval and its accuracy, I agree that in some cases it is relatively accurate. However, I would take it as a guideline only because, when I tried to validate it using data from its official partners, the results were rather scattered from too low to too high. So I fully agree with your comments about pricing of gemstones. In my case as a budding small scale gem seller outside the internet, I just like to offer the gemstones which I buy on the internet at a reasonable price so that both me and the buyer can get a good deal out of the sale.


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 Post subject: Re: gemval historical value?
PostPosted: Tue Jul 29, 2014 10:54 am 
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Joined: Sun Oct 16, 2005 12:22 pm
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Location: San Francisco
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Wow that's a huge wall of text. Sorry about that, I'm on benadryl.

Wow, if I could be that articulate on benadryl, I'd take it every morning. :wink:


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