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 Post subject: Spessartite/Mandarin Garnet difference?
PostPosted: Wed Nov 23, 2022 6:41 pm 
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I have been doing quite a bit of reading and so far I believe that Mandarin is basically another term to describe Spessartite Garnet. Please disabuse me of this if I am mistaken! My wife has recantly purchased two rings with center stones described as Spessartite and Mandarin respectively. I tried diligently to find info on what makes a more "valuable" example and other than the obvious i.e. size, clarity, cut, etc. I can't make heads or tails of it. I assume color is the deciding factor assuming all else is equal, but I've seen pricing all over the map (as in all colored stones) for what seem to me to be similar colored/sized stones. I am attaching vendor supplied images and would appreciate comment/classification as to color ID etc.
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 Post subject: Re: Spessartite/Mandarin Garnet difference?
PostPosted: Wed Nov 23, 2022 11:11 pm 
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Here's an article that may help, maybe you have already seen it.
https://www.gemsociety.org/article/mandarin-garnet/

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 Post subject: Re: Spessartite/Mandarin Garnet difference?
PostPosted: Wed Nov 23, 2022 11:38 pm 
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glhays wrote:
Here's an article that may help, maybe you have already seen it.
https://www.gemsociety.org/article/mandarin-garnet/

Thanks for that! I had seen it but upon re-reading I Think the oval basically "qualifies" as Mandarin and the cushion with it's "brownish modifiers" (if that terminology applies) is simply Spessartite? We are still waiting for their arrival so I'm not sure of color accuracy. For these stones what type of lighting offers best results? Thanks again!
RogerG


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 Post subject: Re: Spessartite/Mandarin Garnet difference?
PostPosted: Thu Nov 24, 2022 12:48 am 
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First you may be interested in the nomenclature to of this species name. Spessartite is a legacy term that was a synonym for Spessartine. The major institutions have now agreed that Spessartine is the correct nomenclature for this gem mineral. Of course this industry being what it is, the use of the term Spessartite is still common. Change happens slowly.

When the original Namibian find of the bright orange color of Spessartine was brought to market large clean stones were very rare and expensive. The local Africans called the best color "Fanta" Garnet after the popular soft drink of that name because the best colors closely approximated the color of Fanta. It was also often called Mandarin Garnet because the color of Mandarin Oranges also matched., and it was thought it was a more premium name than a soft drink.

As is often the case, new deposits of similar material have been located and stones from these areas are now in the market. Notably, the deposits in the Loliondo area of Tanzania has sporadically been a producer of significant quantities. The stones from there range in color from stones that match the best of Namibia to stones with brown and red color components that probably shouldn't be called Fanta/Mandarin but often are in the market. This area also produces larger stones. Many are included with small crystals that the locals call sugari (sugar), that can reduce the brilliance that top Spessartine is value for.

As you have discovered prices in the gemstone industry can vary significantly for a variety of sensible reasons, but also for no apparent reason at all. Specific to your Spessartine value question my guess is that the higher priced firms are referencing the original Fanta/Mandarin Namibian stones when setting prices. Others may be basing pricing based on rough costs from the newer sources such as the Tanzanian stones. A few years ago the Tazanian mines were producing good quantities of high quality stones at very attractive rough prices. I managed to buy a good amount of that production. I imagine that many of the good priced stones you see on the market these days are from that production. Since then the production has been much, much, less. In all cases there are differences in standards of things like color, clarity, and cut, that affect value and pricing.

In short you will need to educate yourself to the market, set your own standards on what you are looking for, and what you are willing to pay for that. Unfortunately, I cannot give more accurate price guidance than that. Top Spessartine is one of my favorite stone. So bright because of the high refractive index. A great gemstone. I wish you the best in your pursuit of a nice stone.

Steve


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 Post subject: Re: Spessartite/Mandarin Garnet difference?
PostPosted: Thu Nov 24, 2022 10:19 am 
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Thanks for that Steve! Since you have an affinity for this variety would you please give your opinion as to whether the oval qualifies as Mandarin or is it too light?


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 Post subject: Re: Spessartite/Mandarin Garnet difference?
PostPosted: Thu Nov 24, 2022 1:14 pm 
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rogerg wrote:
Thanks for that Steve! Since you have an affinity for this variety would you please give your opinion as to whether the oval qualifies as Mandarin or is it too light?


Although it has a little bit more brown than the best of the Fanta/Mandarin color it is within the range of what is currently being sold as better color Mandarin in the market. It appears from the picture to be cleaner than average for a Spessartine, and the cutting is also on the better end.

I hope that information is useful to you.


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 Post subject: Re: Spessartite/Mandarin Garnet difference?
PostPosted: Thu Nov 24, 2022 1:31 pm 
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1bwana1 wrote:
rogerg wrote:
Thanks for that Steve! Since you have an affinity for this variety would you please give your opinion as to whether the oval qualifies as Mandarin or is it too light?


Although it has a little bit more brown than the best of the Fanta/Mandarin color it is within the range of what is currently being sold as better color Mandarin in the market. It appears from the picture to be cleaner than average for a Spessartine, and the cutting is also on the better end.

I hope that information is useful to you.

FOR SURE! Thanks again and happy Thanksgiving!


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 Post subject: Re: Spessartite/Mandarin Garnet difference?
PostPosted: Thu Dec 01, 2022 9:07 pm 
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They arrived this evening and I took a couple of pre-cleaning side by side shots. I think they both look better "in the flesh". Any thoughts on the color classification on the cushion? Photos taken under usb magnifier w/led ring light.


Attachments:
My project (2).jpg
My project (2).jpg [ 420.72 KiB | Viewed 2848 times ]
My project (1).jpg
My project (1).jpg [ 2.21 MiB | Viewed 2848 times ]
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 Post subject: Re: Spessartite/Mandarin Garnet difference?
PostPosted: Wed Dec 07, 2022 10:44 pm 
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Hi Steve, I actually took the stones in to 2 different local "gemologists" today and, surprise surprise, got different readings on the stones. The first guy got RI's of 7.56 on both stones and the second got 7.62 on the cushion and 7.95 on the oval. The oval seemed to give them both trouble which surprised me considering the size of the stones. I thought they'd be easy to read even if not resulting in what was expected. Do those numbers give you any pause as to ID? Also I was hoping you might point me toward a competent cutter willing to polish or re-cut both stones and one of the spinels as the oval and spinel are abraded and need attention.
Thanks as usual!
Roger




Your refractive index numbers make no sense. You have likely left the "1" off the front and they should read 1.756 rather than 7.56.

Assuming the leading "1". The numbers from the first guy at 1.56 and 1.762 are very low for Spessartine garnet, which properly should be near or over the limit of a refractometer which is 1.81. These lower RI numbers indicate that the stones are a mixture of of Spessartine/Pyrope/Almandine garnet, commonaly called "Malaya" Garnet in the trade. The low one could even possibly be a Grossularite Andradite Garnet mix trending toward Hessonite. However, looking at the stones I doubt it in your case. The second numbers are higher, and more what one should expect from a Spessartine Garnet. I am surprised to see such a big disparity between the two Gemmologists. Garnet is a singly refractive stone so good RI reading should never vary more that a few 100s.

It is a very common thing for garnets to be of mixed composition. In fact the vast majority of garnets are solid solution mixes of the various garnet end members. Opinions vary on what percentages a garnet must have to label it as one of the end member garnets such a s Spessartine. That is one reason that it is not good gemological practice to label a garnet species based on RI alone. One should use spectroscopic analysis to make the call.

If you are interested in learning about this my friend Kurt Feral has done extensive research and publishing on the subject. His focus was using magnetism to differentiate the garnets. But his explanation of the issues is easy to understand and worth the read for your.

https://www.gemstonemagnetism.com/template

here is an excellent resource for you by Dr Gubelin who is probably the most respected Gemmologist of our time. You will see pictures of all of the different gem garnets. You can click on the PDF for each and see it full laboratory report. You will see some of the original "Fanta/Mandarin garnets from Namibia and can see what a typical RI is for them. You will also see the other types of orange gem garnets. I think you will find that all of the stones labeled pure Spessartine are either over the limit of the refractometer, or very close to it. Certainly none below 1.790. Also notice the heavy reliance on spectroscopic analysis to make the species calls in Dr Gubelin's reports. R.I. is not sufficient.

https://www.gia.edu/gia-gem-project-garnet

Is it correct to call a stone that is a Spessartine/Pyrope mix a Mandarin garnet based on color alone. I think you will get a wide difference of opinion on this in the trade. You must decide for yourself.

Steve

P.S. I think you may want to post your question and my answer on the thread as it may be of interest to the general membership.


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 Post subject: Re: Spessartite/Mandarin Garnet difference?
PostPosted: Wed Dec 07, 2022 11:18 pm 
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Roger,

Thanks for posting this in an open thread. The subject does present some interesting Gemological questions.

The original Fanta/Mandarin Garnets were in fact Spessartine with typical OTL (Over The Limit) RIs, and a distinctive orange color. This combination of high RI, and color, produced stones of exceptional brilliance and color that were very attractive and commanded high prices. The high prices were the result of the rarity of such a color in Spessartine Garnet.

Currently there are stones with similar color, but because they are actually very mixed species of garnet family end members, they have lower RIs, and consequentially lower brilliance. They are available from a variety of locations, and command lower prices than the original Namibian stones. This cause a great deal of price uncertainty and confusion in the market.

Is it correct to define a stone that is a garnet of a certain orange color but not a Spessartine but a mix, a Fanta/Mandarin Garnet?

Should we insist that stones have an RI close to or above OTL to get the name and the associated price of a Fanta/Mandarin Garnet?

I am interested to hear peoples opinions on this question.

Steve


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