Would some andradite content disqualify a stone from being called a tsavorite if it is in the right color range? Assuming Cr grossular qualifies, though I am not sure how debated that is.
Post subject: Re Post subject: Seperating Tsavorite,Mali ,Grossular-Andrad
Posted: Wed Feb 28, 2018 5:43 pm
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Joined: Mon Jun 16, 2014 1:10 pm Posts: 850
Difficult....
garnets
To my knowledge mali garnet have sometimes a fine green or colorless core with low iron content - and lower RI. And they are rare! Chromian grossular...chromian Mali, chromian Grandite....
Removing a couple variables, how do you feel about the name being applied to, say, the Canadian chrome grossulars that are of essentially equal color quality to a V-colored tsavorite?
Post subject: Re: Post subject: Seperating Tsavorite,Mali ,Grossular-Andra
Posted: Thu Mar 01, 2018 5:26 pm
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Joined: Sun Oct 16, 2005 12:22 pm Posts: 21602 Location: San Francisco
I did as I said and started a new thread. Although all this information is really fascinating (I'm serious, it IS!) we have no additional information from Ross. We don't even know what the mystery stone looks like. No additional inclusion pics. No pic of the actual stone. Maybe all the posts (with the exception of the first couple) should be moved to a thread called Green Chrome Grossulars and their Varieties
Yeah, I was just trying to get some juice out of the thread while we wait. It's an interesting topic, and while I'm sure emotions about the definition run high in some circles I haven't seen any fighting or name-calling like I have over, say, what qualifies as imperial topaz.
Post subject: Re: Post subject: Seperating Tsavorite,Mali ,Grossular-Andra
Posted: Thu Mar 01, 2018 6:17 pm
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Joined: Sun Oct 16, 2005 12:22 pm Posts: 21602 Location: San Francisco
Total success Stephen. Too interesting not to have its own platform! I'm going to make a new thread. Let's add some pictures and other points of interest on chrome grossular.
PS The color of precious topaz is an opinion, like padpradscha and with some (cough cough) alexandrite.
The posted example of chrome grossular doesn't have sufficient color quality either way. But can you tell me just by looking which of these is chrome grossular and which is vanadian grossular? Certainly not from quality of color.
In addition to the madagascar deposit mentioned in the article and the tiny canadian production bits of grossular in the same color range come out of Afghanistan from time to time, but I don't know what the colorants have proven to be. They don't seem to have been enough to significantly affect the market but they may find more one day.
Personally I think this situation is reasonably analogous to emerald and the various debates over Cr/V. In the end I think trying to divide emerald from vanadian green beryl was regrettable, and it would be better to not make the same mistake again. I guess my stance would generally be that gem varietal names should be defined based on basic gemological properties (ie, species, color, phenomena, etc).
I've conveniently left "basic gemological properties" without a specific definition, since these vague principles run into difficulty when you get into the intricacies of, say, paraiba tourmaline, but at least the chromophore there is (per proponents) tied to a color quality unattainable with other chromophores. And they don't help that much with how to deal with cases like 'grandite', since its SG/RI are distinct from either endmember. But generally speaking, if it has sufficiently fine green color and it's majority grossular then I'd probably want to call it tsavorite. The amount of Mali garnet that would qualify would be so minor it wouldn't matter much either way anyway.
Of course for future predictions the one that's on the horizon right now is probably the Ethiopian green grossular (picture from Tucson last year, saw the similar but larger parcels this year).
For now it's small material with a very heft pricetag (400/g!!!) that nobody seems interested in paying. But if production increases there will likely be at least some pressure in the market to sell it as tsavorite (by which I mean it's already being sold as tsavorite, but nobody cares yet). I think we'll agree that the pictured stones don't match either of our definitions. On the other hand 'grossular' doesn't have the best ring, so something will probably have to be done there.
Post subject: Re: Seperating Tsavorite,Mali ,Grossular-Andradite Mix Garne
Posted: Fri Mar 02, 2018 3:49 am
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Joined: Mon Jun 16, 2014 1:10 pm Posts: 850
I agree 100 % !
The first crystal mix in a parcel of tsavorites from Kenia/Tanzanis - no doubt from this color tsavorite would be ok.
I am a bit careful judging from pics - really difficult to get rhe right color.
I have to tiny afghan "Tsavorites" and a parcel bought from GSK from Jeffreys Mine Canada - try to make pic. The canadian stones are soooo close and quite large so I don't whether rhey are really from Canada....
But some show pink fluorescence (LW). Only a small amount of eastafrican Tsavo show fluorescence ( low iron and enough chromium).
Post subject: Re: Seperating Tsavorite,Mali ,Grossular-Andradite Mix Garne
Posted: Sat Jun 01, 2019 4:08 pm
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Joined: Mon Apr 16, 2018 7:25 am Posts: 38
Interesting thread. Bumping it up, because I'm curious about a garnet specimen I bought today. It was actually sold as peridot from India (!), but it's green garnets in some sort of serpentine-type matrix:
The green is actually livelier in person than it appears on that photo. These garnets show a colour shift too, from a beautiful mint green in daylight to a more lime/olive green in incandescent light. This property together with the matrix they are in leads me to believe that this specimen is from Ghazni Province, Afghanistan. All the specimens from this location I can see for sale or on Mindat suggest that these garnets are andradite var. demantoid, but another Mindat member has suggested that they may in fact be grossular. Does anyone else here know for sure?
Colour shift would suggest that Cr or V (or both) may be the chromophore. I don't know of iron causing colour shift in crystals. If these garnets are grossular and contain V/Cr, then technically, I suppose they could be called tsavorite.
Last edited by Nick_G on Sun Jun 02, 2019 11:52 am, edited 2 times in total.
Post subject: Re: Seperating Tsavorite,Mali ,Grossular-Andradite Mix Garne
Posted: Sun Jun 02, 2019 3:26 am
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Joined: Mon Apr 16, 2018 7:25 am Posts: 38
Well, a member on another forum has a green garnet from very probably the same locality as my specimen and analysis showed it was almost pure end-member andradite. So I presume this is what I have as well.
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