Demantoids

[minousbijoux]

Okay - I'll start by saying I'm sorry for no pictures - please forgive.

Yesterday, at Intergem, one of the vendors had a set of Russian demantoids. The vendor was excited to have them as he gets them rarely from a collector who periodically sells some of his holdings. They were beautiful! Three round brilliants - two of them were a little over a ct each, and the big one was about 2.3 cts. The color was this intense, saturated green - almost like a tsavorite with a slight yellowish modifier. They were sparkly and reminded me of Spring. But the horsetails were what blew me away; the stones appeared completely clean except for the horsetails, like someone had dropped in one or two of these bursting fireworks. One or two were perfectly formed, with all the wisps (or whatever you call them) drooping over just like, well, horsetails!

The vendor was excitedly imagining that someone would buy them all together and set them in a ring. Its the most excited I've seen him about any of his stones. He was willing to break up the set for me, but his prices are very high, and before I leap at another stone (or two) that I love and forego the kitchen remodel (slight exaggeration, but you know what I mean), I thought I would ask you, the experts.

Do you think I could find some elsewhere, say Pala? Any idea of a price range for a 1 carat, well cut, well saturated green, green Russian demantoid with classic horsetails? How do I go about even finding comparison stones?

TIA

 

[Edward Bristol]

5-10k/carat in round one-carats.

 

[chrono]

Litnon used to carry a great quantity of Russian demantoids but not so many nice ones lately.

 

[Arkteia]

5-10k/carat in round one-carats.

I'd say, depends on where you buy, but I bought mine (2.3 ct) in that price range. It was three years ago.

Good luck, Minous! If I saw a stone like the one you described, I'd have to be handcuffed not to pull out my credit card...

P.S. So you did go to that Bay Area Intergem!

 

[VapidLapid]

I second Chrono's mention that litnon used to have a good selection of those. Perhaps they have some still that are not on the site? I have some demantoids from them, quite recent too. One is Russian and two are Namibian. While they look more like peridot than tsavorite, they cost less than peridot. Gemfix has had some stunning Russian demantoids that I am still kicking myself for not having gotten; they too might have more for the asking.
Here are some pics of mine from litnon, .57 ct, and 2 x .16 ct.

 

[VapidLapid]

 

[canuk-gal]

HI:

I'd also love a pair or three-- . The pair on Wildfish are dreamy. Major bucks.

cheers--Sharon

 

[minousbijoux]

Well if I remember right, he was offering the smaller ones for $5,500/ct (which I thought was astronomical but what do I know?!!) and the 2+ carater for around $12,000/ct (can't remember this price, could've been slightly less, and know it wasn't more).

Maybe installment payments?

 

[Arkteia]

The prices are probably representative of what the market offers now.

 

[minousbijoux]

Pandora, are you around? I was hoping you would weigh in as the garnet expert.

In the meantime, I appreciate everyone else's wisdom. Crasru, are there pics somewhere of your demantoid? I would love to see it. TIA

 

[Pandora II]

I am around - and have been doing some detective work as I thought that they were a little on the expensive side...

Do you know if they are heated or not? A lot of demantoid is these days.

You will pay a premium for Russian origin and even more for good horsetail inclusions, but even so.

I got my friend to check a few on Pala and they were coming in at around the $4k/ct mark for 1ct. However, if the ones you saw were a matched pair then $5.5k is reasonable as pairs always command a sizeable premium.

The larger stone is more appropriately priced. He only looked at top colour with horsetails for me (only Russian stones have horsetails), they were heated though. Pala is generally top whack so any more than them always gets my eyebrows raised a bit.

However, I haven't seen them to be able to judge just how good they are, nor have I seen the Pala stones other than in a photograph, but I trust my friend to know what he's looking at. Fine Russian demantoid is rare and you are going to shell out a lot.

Hope that helps a bit.

 

[TonyMontana]

If its a russian demantoid you can be more or less sure its been heated. You can find inclusions which resemble ''horsetails'' from other localties aswell, however I haven't seen a Demantoid with a well formed horsetail which wasn't of russian origin, so it is a good indication of russian origin. In my opinion russian demantoid is horrible overpriced compared to fine Demantoids from other deposits and I personly wouldn't buy a Demantoid with a horsetail at all. But anyway If you want my advise: Try to get a horsetail which is in the center(!) and despite the horsetail the stone must have some fire, so it should be well cut and as clean as possible! Furthermore Demantoid is a very difficult stone to photograph so naturally try to see the stone before you buy it Excpect about 5k/ct for a nice 1-2ct stone. Pala indeed has a big inventory of russian demantoid and you most likely find something you like there.

 

[minousbijoux]

Thank you both for your posts.

Pandora: thanks for the detective work. I'm not surprised that Pala would have them cheaper, as this guy tends to have very, very high quality, and very, very high prices - or so it seems to me (not questioning the quality, just the pricing). Litnon does have one for $1,700 which apparently has a horsetail, but the pics don't seem any where near as nice as the ones I saw. Perhaps I can get them to send me photographs of the stones. It would also be good to see them away from the special make-everything-sparkle-and-gleam gem show lighting.

As to heating, does heating have a bearing on the price of demantoid? I know you'll get a kick out of this, but my first reaction to your question was to respond with "oh, I know they're not heated because I know and trust the seller, and he knows and trusts the collector who has had the stones for a long time..." Hee hee, but I caught myself!

 

[Pandora II]

You might find this interesting: http://www.palagems.com/demantoid_disclose.htm

• GIA – Will not identify whether a demantoid garnet has been heat treated; will not determine origin on demantoid garnets
• AGTA – Enhancements: Indications of heating. Gemstones of this type may be heated to improve their appearance. This treatment is not detectable using current technologies; such heating is generally stable under normal wearing conditions. AGTA is not giving country of origin
• AGL – AGL will make the heating call, and give country of origin :
“It is in the opinion of the Laboratory, based on the weight of evidence, that the origin of this material would be classified as Russian. It is the opinion of the Laboratory that this material has been subjected to a low to moderate heat enhancement process to produce a permanent and stable color.”
• Gübelin Gemmological Laboratories – Will denote the country of origin but not whether the material has been subjected to heat
• SSEF Swiss Gemmological Institute – Will state country of origin and whether there are indications of heat treatment

So amongst what I consider to be the best labs in the world, there are big differences. I don't recall ever seeing demantoid being sold with an 'ooh and it's unheated' which combined with the fact that GIA, AGTA and Gubelin won't test for it makes me think that it probably doesn't have much of an effect on price.

But I'm also not someone who is buying top demantoids (sadly) so I haven't actually put any real thought into it. I will go away and seek advice from others as it's an interesting point especially as some labs do report and some don't.

 

[minousbijoux]

You know, it just never even occured to me to ask about treatments I was so stunned by the beauty of these stones...

 

[Lovinggems]

At least get the large one if it's within budget , but be very careful if you want to set it.

 

[chrono]

It is my understanding that horsetail inclusions can also be found in non-Russian material and that almost all demantoids are now routinely heat treated, with this treatment not being easily detectable. Pricing seems rather on the high side...

 

[TonyMontana]

Well thats not entirly correct. All russian demantoid is routinely heated or somehow treated to alter the color. As with other gemstones sometimes it alters the color and sometimes not. Demantoids from other locations don't respond to heating as the russian material does. Don't know why. Maybe because it simply doesn't work or the methods used by the russians are so sophisticated that other dealers haven't figuered it out yet. I know for a fact that the biggest supplier for namibian Demantoid doesn't treat their stones in any way to enhance the color. Thai dealers tried it with mada Demantoid and failed. So not all Demantoid is heated (yet) just the russian stones!

 

[Pandora II]

Well thats not entirly correct. All russian demantoid is routinely heated or somehow treated to alter the color. As with other gemstones sometimes it alters the color and sometimes not. Demantoids from other locations don't respond to heating as the russian material does. Don't know why. Maybe because it simply doesn't work or the methods used by the russians are so sophisticated that other dealers haven't figuered it out yet. I know for a fact that the biggest supplier for namibian Demantoid doesn't treat their stones in any way to enhance the color. Thai dealers tried it with mada Demantoid and failed. So not all Demantoid is heated (yet) just the russian stones!

I'd agree with Tony.

I've been talking to someone who did serious research experimenting with heat-treating demantoids and said that it didn't change the colour it just made them split...

 

[GemFever]

Hello everyone,

This is my first post here ever I have been reading up on some threads though, and doing some research. Couldn't resist posting about my demantoid.

I got it off ebay (grandgemstones) this summer, and I'm pretty happy with it. It's a 2.43ct oval, I got it for $215. I'm kicking myself for not recording all the specs before the listing was removed, but I'm pretty sure it's African. It's very clean, with just a tiny white inclusion under the table (not really visible when you wear it). The fire is amazing under the right light conditions (it fires at the same time when my AVC does ), the color is a nice grassy green. It was a summer evening when I first got it, still light outside, but I already had the lights on in the house when I photographed it. I was surprised that the stone got confused about the light--half of it turned olive, and the other a rich teal green. Usually it's more balanced though.

Let me see if I can include two pictures (the confused lighting, and on the hand). What do you think of it? I know it's not Russian (though I am ), no horsetails or anything.

 

[ASA]

The fact is that most Russian Demantoids are not heated. There is a color that the Russians call flavovirent, kind of a mossy yellow green that will respond to heat by driving out ~some~ of the undesirable secondary hues. Even then the stones are not as nicely colored as the ones wth a higher chrome content.

Also heating a Demantoid to the temperature needed to enhance the color will turn white Byssolite (horsetail) inclusions dark brown to black. If you look at rough photo's of Demantoid on Pala's website you can see the natural color of the rough including a specimen still attached to matrix.

Michael - Gemline inc.

 

[minousbijoux]

Wow, that is really interesting - so if these horsetails were white does that mean it likely was not heat treated?

 

[ASA]

Yes, the horsetails will darken when heated and white is a good indication that it has not been heated Also if the color is already a nice chrome green it means the stone probably has not been heat treated as well. The flavovirent color is the only one that benefits from heat treating and even then the improvement in color is modest... IMO

 

[TonyMontana]

Yes, the horsetails will darken when heated and white is a good indication that it has not been heated Also if the color is already a nice chrome green it means the stone probably has not been heat treated as well. The flavovirent color is the only one that benefits from heat treating and even then the improvement in color is modest... IMO

Sorry Michael but I disagree with you. Most russian Demantoid is heated. The color which benefits the most is turning Brown Andradite into green Demantoid via heating/treating it. I wouldn't call a color modification from Brown to green ''modest''. Haven't heard of the term ''flavovirent'' either but I can ensure you it isn't russian.

 

[Pandora II]

I've been having a discussion on this with some other people and what has come out so far has been quite interesting... to protect people's privacy I am not going to give any names, but these are all extremely well-qualified gemmologists - some from the bigger gem labs, so I think their comments are to be considered very seriously.

For starters, AGL will only classify an Andradite Garnet as a Demantoid if the colour is primarily due to Chromium, if it is primarily due to Iron then it is an Andradite Garnet and not a Demantoid (most Madagascan stones are coloured by iron even if they are green). And here starts another Emerald v Green Beryl war...

Next, one of the participants had the possibility to inspect a fair number of heated and unheated demantoids at Munich, and was unable to see any difference in the horsetails between the two. He was also informed by the Russian dealer that the great majority of demantoids from Russia are now heated - although type of heating differs depending on source and individual characteristics.

Apparently it's only worth treating the Russian stones, doesn't work on those from Iran, Namibia or Madagascar.

One of the big labs says that detection of heat treatment is difficult, sometimes you can see atol-like discoids along some of the fibers, spectroscopy can also sometimes detect differences.

So far no-one has mentioned any effect on pricing.

 

[chrono]

Thanks for the update, Pandora. I also hear/read conflicting reports which I guess is still ongoing as to what's being heated/not heated, how to detect heating, nomenclature and etc.

 

[ASA]

Sorry Tony but I have considerable experience with Russian Demantoid and respectfully disagree with you. The Russian term желто-зеленый, is the word used by our Russian supplier (and miner) to describe the color of Demantoid that responds best to heat treatment. It translates to Flavovirent.

I am not going to argue the point. Perhaps our Russian friend is mistaken. But until someone more qualified than he tells me different... I am going to accept his explanation to me about Demantoid heat treatment.