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 Post subject: Re: Spodumene Investigation
PostPosted: Mon Oct 13, 2014 7:57 pm 
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Scarodactyl wrote:
Alnitak wrote:
The sources of color in minerals is fascinating...I have toyed with the idea of going back to grad school to study the topic, but I'm bit too old for that I think.

I'd love to work on that as well. Alas, you'd have to be really lucky to find a place and an advisor that would actually allow for studying it. Trace element analyses aren't free, after all. Probably the sort of pursuit what would be best accomplished by the independently wealthy.


I lived in LA from 2007 through late 2013 and got to meet Dr. George Rossman from CalTech at the MSSC club meetings. I should have just stayed in LA and studied with him--its his area of expertise. Sigh.

Jeff

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 Post subject: Re: Spodumene Investigation
PostPosted: Tue Oct 14, 2014 6:51 am 
This is a little info from Frank, my stone cutter in Pa. "Steve, Greetings! Kunzite will intrinsically have a moderate to strong pink to orange flourescence under Long Wave and the same but weaker under Short Wave. The only definitive test that GIA lists for seperation between natural and irradiated is a prolonged "fade test" with exposure to UV and or possibly a reading via a Geiger counter.
I wouldn't put to much UV on any Kunzite. I hope all is well. Thanks, Frank", I think this info will add to the overall story being gathered or learned on this unusual stone, steve... :smt003 :smt001 but still 8)


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 Post subject: Re: Spodumene Investigation
PostPosted: Thu Nov 06, 2014 12:17 pm 
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Here's a real oddity I hadn't heard of before: citrine-colored (Yellow-orange to greenish yellow) spodumene irradiated in a linear accelerator:
http://www.gia.edu/gems-gemology/summer ... ne-rossman
Weird: unprecedented color in my experience.
weirder: they were mixed in with a parcel of citrine and sold as such.
weirder still: it was a parcel of cut stones, so there's no way they didn't know it wasn't citrine at least at some point. Yet they sold it as citrine? Wat??
weirdest: potentially unsafe levels of residual radiation.

No word on color stability or the persistence of the radiation. I would guess that those particular stones are probably safe now (since the paper is from the 80s) but you never know.

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 Post subject: Re: Spodumene Investigation
PostPosted: Fri Nov 07, 2014 12:02 am 
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terrific


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 Post subject: Re: Spodumene Investigation
PostPosted: Sun Nov 23, 2014 1:58 am 
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Two quick notes on fluorescence.
First, I was looking at one of my yellow spodumenes and I noticed that there is a sharp discontinuity in its fluorescence--it has a dividing line between bright orange and pale fluorescence, clearly a phantom of sorts. No change in color from one side to the other. Photos to follow if I can get it to show up.
And I also came across this photo from John Betts: a (sold) green-pink bicolor where the green portion is either nonfluorescent or at least much less fluorescent than the pink portion. Huh.
http://www.johnbetts-fineminerals.com/j ... p?id=36700

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 Post subject: Re: Spodumene Investigation
PostPosted: Sun Dec 07, 2014 12:42 am 
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So, I recently bought a parcel of yellow and yellow-green spodumenes, along with a huge parcel of mixed colors. I've had a few samples in the sun for a few weeks now and seen no change. Some of the greens are really quite green--not hiddenite green but getting there. These seem to be examples of the third green spodumene, an offshoot of the triphane branch and probably at least partially colored by iron. This is ground that's been covered but I finally got some that are a more pleasant green.
Image
How it looks in its best lighting (this stuff shifts, not as bad as pure yellow though).
Image
More typical lighting.
These beautiful yellow-green/spring green stones fluoresce very red under longwave. Some of my yellows and yellow-greens make up the most aggressive fluorescers of my (now very large) collection of spodumene under shortwave relative even to pinks and purples, though some of them are totally dead too. I also found a beautiful aqua-blue stone which doesn't do much of anything under longwave, though goodness knows it will be very unstable in sunlight. I don't know why that is but there you have it.
I also just got in some Brazilian "hiddenite"--they're a pale but distinct minty green, and we'll see if they're stable chromian or unstable Mnian. They fluoresce but only a little bit, as with some confirmed stable Brazilian chrome spodumene. Even if they're stable I don't know if I'd call them hiddenite--they're probably too pale in my book.
Image
Image
This is the most saturated one of the parcel. I'll report on stability once I know.

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 Post subject: Re: Spodumene Investigation
PostPosted: Sun Dec 07, 2014 2:29 pm 
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 Post subject: Re: Spodumene Investigation
PostPosted: Wed Dec 10, 2014 11:54 pm 
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Normally I wouldn't call it this soon--I'd take a few weeks in the sun. But I'm going to call it early because
a) irradiated green spodumene is highly unstable in light, and even in the dark. b) it's getting really cold and they had ice on them when I checked. I don't want them to freeze-thaw cycle and break.
So I'm tentatively calling them totally stable! They showed absolutely no change from a few days in the sun--admittedly some were cloudy, but at least one was sunny all day long.
Pleochroism is different from unstable green spod, which in my experience is blue/green dichroic. Instead, it is green/yellow dichroic.
Another fun fact: under outdoor or incandescent they are a nice minty bluish green. But under fluorescent the green is really kicked up, and is a more pure green green. I suspect that this is because it's part hiddenite (Cr or V) and part triphane (Fe). The yellow Fe component becomes much more apparent under fluorescent (as it does) and makes it go from "yeah" to "yeah!"

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 Post subject: Re: Spodumene Investigation
PostPosted: Mon Dec 15, 2014 10:47 pm 
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So, here's a question for you more experienced people out there:
This is a quote from the Fall 2007 issue of G&G article "Cr/V-bearing green spodumene from Afghanistan.":
"To our knowledge, Cr-bearing spodumene is now known from Brazil, India, Siberia, and Afghanistan, in addition to the original area near Hiddenite, North Carolina."
So, I know the Afghan stuff--I've got a few pieces and more coming in the mail. I know the Brazilian material and I have a few pieces (plus some nice facet rough!) I've also heard one other reference to hiddenite coming from India, as well as one other to Siberia. But that's it--a couple of offhand references in sources which were mostly garbage. I discounted them until I saw this mention while rereading this article. No doubt these finds were before my time, and google isn't being much help. Does anyone else know anything about these references?
I've also seen a few references to a find in Madagascar (though these seem to actually be greenish triphane from the description I read, but you never know), as well as one in Sri Lanka (hard to discount out of hand because there's almost nothing not found there).

Edit: ok, I found a reference on the Indian stuff: "On an occurrence of hiddenite from a pegmatite near kabbur, hassan district, Mysore india" (Current Science 1975). From what I've seen, that's the only data out there--a short article that mentions hiddenite (ranging from apple to emerald green) is found there. Huh. I want some but I have no idea if it was ever properly collected or appreciated. Google isn't getting me anywhere. I have to wonder whether the find was actually legitimate.
Babu, S. K. 1975. On an occurrence of hiddenite from a pegmatite near Kabbur, Hassan district, Mysore State. Current Science 44:387-88.

edit2: I found a citation for the Siberian find but am having trouble finding the paper itself.

Samsonova, N. S., and V. G. Feklichev. 1962. Hiddenite from the Siberian granitic pegmatites. Transactions of the Institute of Mineralogy, Geochemistry and Crystallochemistry, Akadamy Nauk SSSR 8:197-200.

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 Post subject: Re: Spodumene Investigation
PostPosted: Sat Jan 03, 2015 1:04 pm 
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This is probably as good a thread as any for this. I just got in a nice parcel of Afghan hiddenite, showing a range from saturated yellow-green to saturated emerald green, with a bit of a range in between.
Image
Pictured here with my most saturated Brazilian hiddenite--they look really lovely on their own, but pale before this significantly more saturated material. They still have size on their side, anyway.
Image
This one shows very sharp color zoning, yellow-green to emerald green.
Image
The yellower stones pictured with a yellow-green spodumene which likely has no trace of Cr or V. The big one really does have quite a bit of green to it as pictured above--once again, though, the color pales before the genuine article.
Anyway, I'm pretty excited about these stones. If there is interest I could put a few on the marketplace as facet rough or as specimens, but otherwise I'll try to have a few cut and save the rest, probably mostly to annoy other North Carolinians.

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 Post subject: Re: Spodumene Investigation
PostPosted: Sat Jan 03, 2015 4:54 pm 
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Scarodactyl, how big are your spodumenes?


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 Post subject: Re: Spodumene Investigation
PostPosted: Sat Jan 03, 2015 5:41 pm 
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Not terribly large, unfortunately (the hiddenites, anyway--I do have some giant spods), but good for the species. The saturated Afghan ones range from 2.5 to 26.8 cts, though few are flawless (they're pretty clean overall, though). The paler Brazilian ones go from 26 to 102 cts, and are almost flawless except for the second-largest.
Image

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 Post subject: Re: Spodumene Investigation
PostPosted: Sat Jan 03, 2015 6:05 pm 
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You can still make some nice gemstones out of the rough you have. I do prefer the more saturated crystals from Afghanistan though. Am I correct to assume that the green spodumene from Afghanistan tends to be smaller than the purple-yellow one (kunzite) from the same country?


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 Post subject: Re: Spodumene Investigation
PostPosted: Sat Jan 03, 2015 6:35 pm 
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Yup, I'm afraid so. I'm not 100% convinced when people say chromium is a growth inhibitor, but regardless of location deep green hiddenites never seem to be very large, similar to emeralds. The Afghan material also comes from a completely different mine than the larger, Cr-free spodumenes.

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 Post subject: Re: Spodumene Investigation
PostPosted: Sat Jan 23, 2021 5:14 am 
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Good day all,
Would love to reopen this thread and ask a couple of questions to all you experienced gemos.

I have just finished cutting material very similar to Stephens Afghan material shown above. It does seem to be stable(several days in the sun), it is from afghanistan(as per the Afghani seller of the rough), and it DOES fluoresce(pink-orange).
Now here is the question, if this was colored by Chromium it would NOT fluoresce correct?
The color under natural light and under UV light is very very similar to some top colored merelani Mint Garnets.

So my assumption is that the chromophore for this material is Vanadium (my fav!) and hence the fluor and the stableness of the material?

what you all think? how can I test the theory myself if at all?


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