Strange Stone - Vanadium Chrysoberyl

[Barrett]

LOL..here is another wrench, LD..toss it into the discussion...LOL..more questions than answers now

 

[Barrett]

I don''t know squat about chryso or alex for that matter so I love the info you and the others are providing..this is how we learn..this is what threads are all about..

 

[oddoneout]

Very interesting stone.

 

[Kismet]

Date: 4/5/2010 12:33:44 PM
Author: Kismet

Date: 4/5/2010 12:24:39 PM

Author: LovingDiamonds

Brilliant photo and lovely stone Kismet. Thank you for sharing.



Well the first difference is obvious - you can photograph it and capture the green! The second difference is that yours is far more green than mine. I''d love to know if yours has fluor or not. Would it be too much trouble to ask you to look for me please? I wonder if that''s the difference between the two????

Sure I can check for you when I get home. If it does fluoresce, no guarantees on a picture. I haven''t been able to take a decent picture under black light yet; mine all come out purple or way over exposed or both.

Well I whipped out the black light as soon as I got home and none of my chrysoberyls fluoresce. My little alex cat''s eye does fluoresce red.

 

[zeolite]

LD's reference: The color change phenomena is a result of the presence of chromium +3 ions and the way they are absorbed and reflected…In alexandrite, where the band is at 580nm and right between ruby red and green emerald, the stone is balanced between them. When the light is balanced (daylight), the stone will be green but when the light source is reddish (incandescent), the stone appears red.

My comment: in my 30+ years as a physicist, I have learned wavelengths vs colors. If you give me any wavelength in nm (nanometers), without looking it up, I can tell you what the color is. 580 nm is yellow golden, and that is exactly the band where it needs to be, to make a color change stone.


LD's reference: In practice, chrysoberyl and alexandrite may be difficult to differentiate. Since stones with a weak change may be called alexandrite and stones with a faint change are called chrysoberyl, what is the difference? Where is the borderline?

My comment: I have a minor nit to pick with this. All alexandrite is a special case of chyrsoberyl. So all alexandrites are chrysoberyls, but not all chrysoberyls are alexandrites.

LD's reference: Fluorescence is another property to help us differentiate. Chrysoberyl owns its yellowish color to iron and usually shows no fluorescence. The red fluorescence of alexandrite can be observed using the “crossed filter” method and it has been inferred that in border line cases the presence of a red glow and a faint chromium spectrum absorption spectrum would prove the stone to be alexandrite and not chrysoberyl.

My comment: This doesn't apply to diamonds, but to many colored stones: The main criteria for fluorescence is the presence of chromium and the absence of iron. This is because the presence of iron stops the fluorescence.

Rubies often fluorescence because they are colored by chromium and contain very low or no detectable iron. No garnets (that I can readily recall) fluoresce, because they always contain some iron. The principal metal in the almandite garnet formula is iron, and while the main metal in grossular is calcium, and the main metal in pyrope is magnesium, both always contain some iron.

So - chrysoberyl should not fluoresce since (above) it owes its color to iron. LD's vanadium grossular, would probably be classified as an alexandrite, because the strong fluorescense is proof of extremely low or no detectable iron.

 

[PumpkinPie]

Date: 4/5/2010 12:17:45 PM
Author: Kismet
This is my vanadium chrysoberyl. The picture is mostly accurate; the color is pretty spot on just not as saturated as the picture implies.

that`s a fabulous ring Kismet!

 

[PumpkinPie]

Date: 4/5/2010 4:26:23 PM
Author: stepcutgirl
I have nothing to add. Just wanted to tell you I really like it!

ditto - it`s fabulously cool how much it changes colour

 

[T L]

Date: 4/5/2010 6:16:50 PM
Author: zeolite
This is because the presence of iron stops the fluorescence.


Rubies often fluorescence because they are colored by chromium and contain very low or no detectable iron. No garnets (that I can readily recall) fluoresce, because they always contain some iron. The principal metal in the almandite garnet formula is iron, and while the main metal in grossular is calcium, and the main metal in pyrope is magnesium, both always contain some iron.


So - chrysoberyl should not fluoresce since (above) it owes its color to iron. LD's vanadium grossular, would probably be classified as an alexandrite, because the strong fluorescense is proof of extremely low or no detectable iron.

That is fascinating. Are there any other elements that stop fluorescence besides iron? Perhaps that's why some chromium bearing stones fluor and others do not. I never knew why some did and some did not. This is a "light bulb" moment!

LD,
Sounds like you do have an alexandrite there. I think they find YOU, instead of you finding them now. LOL!!

Zeolite, some grossulars do fluoresce, so does this mean they contain little or no iron?

 

[zeolite]

Date: 4/5/2010 9:10:34 PM
Author: tourmaline_lover

That is fascinating. Are there any other elements that stop fluorescence besides iron? Perhaps that''s why some chromium bearing stones fluor and others do not. I never knew why some did and some did not. This is a ''light bulb'' moment!

LD,
Sounds like you do have an alexandrite there. I think they find YOU, instead of you finding them now. LOL!!

Zeolite, some grossulars do fluoresce, so does this mean they contain little or no iron?

No other elements that I am aware of. Here are two links connecting iron with quenching fluorescence:

http://www.minerant.org/gallery1.html
CALCITE, Santa Eulalia, Mexico
… Under daylight the crystals exhibit a dark brown color suggesting the presence of iron- or manganese-ions. It is well-known that the presence of iron in a crystal acts as a fluorescence-killer.

http://www.faqs.org/patents/app/20090051897

[0036]FIG. 5 is a plot or graph of the wavelength versus intensity for a number of natural and synthetic ruby elements exposed to a red light incident light source. Again, the red LED incident light source peaking at 635 nanometers is shown at line 60. A natural Be treated ruby is shown at line 62, a natural treated ruby from Burma is shown at line 64 and a synthetic flame fusion ruby is shown at line 65. Be treated rubies usually start out as a poor coloured sapphire, often iron quenched, thus explaining the poor red fluorescence shown here.

Hmmm, grossular fluoresces? Can you list a link?

I have an obscene amount of garnets. I just tested 63 of my garnets, including 23 grossulars and 9 color change garnets. Not one will fluoresce.

I tested my 3 chrysoberyls; not one would fluoresce.

I tested 10 spinels; 3 would fluoresce. One weak one was a Tanzanian mahenge pink-orange spinel. It fluoresces weakly. My two hyper-intense Burmese flame spinels fluoresce VERY strongly.

I tested 20 sapphires and one ruby. Since blue and purple sapphires are colored by titanium and iron, you don''t expect them to fluoresce, you expect the pink ones to do so. All if my pinks fluoresced, some weakly, some very strongly.

 

[T L]

Date: 4/5/2010 10:18:51 PM
Author: zeolite

Date: 4/5/2010 9:10:34 PM

Author: tourmaline_lover


That is fascinating. Are there any other elements that stop fluorescence besides iron? Perhaps that's why some chromium bearing stones fluor and others do not. I never knew why some did and some did not. This is a 'light bulb' moment!


LD,

Sounds like you do have an alexandrite there. I think they find YOU, instead of you finding them now. LOL!!


Zeolite, some grossulars do fluoresce, so does this mean they contain little or no iron?

No other elements that I am aware of. Here are two links connecting iron with quenching fluorescence:


http://www.minerant.org/gallery1.html

CALCITE, Santa Eulalia, Mexico

… Under daylight the crystals exhibit a dark brown color suggesting the presence of iron- or manganese-ions. It is well-known that the presence of iron in a crystal acts as a fluorescence-killer.

http://www.faqs.org/patents/app/20090051897

[0036]FIG. 5 is a plot or graph of the wavelength versus intensity for a number of natural and synthetic ruby elements exposed to a red light incident light source. Again, the red LED incident light source peaking at 635 nanometers is shown at line 60. A natural Be treated ruby is shown at line 62, a natural treated ruby from Burma is shown at line 64 and a synthetic flame fusion ruby is shown at line 65. Be treated rubies usually start out as a poor coloured sapphire, often iron quenched, thus explaining the poor red fluorescence shown here.

Hmmm, grossular fluoresces? Can you list a link?


I have an obscene amount of garnets. I just tested 63 of my garnets, including 23 grossulars and 9 color change garnets. Not one will fluoresce.


I tested my 3 chrysoberyls; not one would fluoresce.


I tested 10 spinels; 3 would fluoresce. One weak one was a Tanzanian mahenge pink-orange spinel. It fluoresces weakly. My two hyper-intense Burmese flame spinels fluoresce VERY strongly.


I tested 20 sapphires and one ruby. Since blue and purple sapphires are colored by titanium and iron, you don't expect them to fluoresce, you expect the pink ones to do so. All if my pinks fluoresced, some weakly, some very strongly.

Yes, my grossular fluoresces, and there is a link outside this forum, but I cannot post it here. It is due to chromium. Here is a snippet of what I've been told about this.


The evidence here suggests the absorption band for the green grossular that leads to fluorescence is very close to 400nm. This is not to say that the green grossular can't absorb UV light. But that absorption is not followed by relaxation and emission at longer wavelength. The energetics may suggest it is possible, but the mechanics apparently don't favor this process.

Yes probably the grossular's yellow emission covers a broad range. The orange emission due to 400nm absorption certainly does. One of these days I'll get around to collecting the yellow light's inelastic emission spectrum. Maybe you are suggesting the yellow and orange light is emitted by decay of the same set of metastable states with different population distributions? Maybe so... it is chromium, after all. But just as ruby fluorescence is produced by three separate absorption bands in the visible and UV, these fluorescence here are also populated by separated absorption bands.

The orange emission IS produced by 400nm +/- 20nm light, and the yellow emission IS produced by 290nm +/- 20nm light. But neither the yellow nor the orange emission is produced by 355nm +/- 25nm light. One absorption band is not simply a continuation of the other because of the break at 330-380nm.

And just to be complete, neither the yellow nor the orange emission can be produced by 250nm +/- 20nm light.


Sorry for the threadjack LD.

Mr. Zeolite, we should probably open a new thread if you want to discuss further. Speaking of LD, I think her tsavorite fluoresces as well.

 

[zeolite]

TL: Zeolite, some grossulars do fluoresce, so does this mean they contain little or no iron?

Some garnets tend to mix together easily. Iron, magnesium and manganese tend to mix freely together to make almandite, pyrope and spessartite mixtures.

However, grossulars from East Africa tend to be very pure. They tend to mix only with andradite, and rarely at that. Why?

Formula for grossular: Ca3Al2(SiO4)3

Formula for andradite: Ca3Fe2(SiO4)3

One element in the formula for both is CA (calcium). East Africa was a shallow sea millions of years ago. Sea shells and other animals died and fell to the sea bottom, forming thick layers very high in sea shells (calcium) and at the same time, extremely low in iron (which is universal in most areas of the world's top layer (the crust).

This is the reason why East Africa has the highest quality grossular garnets in the world, why andradite is rare there (an absence of iron, even though there is plenty of calcium). It is also why the finest pink garnets are found there (again the deficiency of iron in a calcium rich sea bed). Anywhere else in the world, the garnets would be deep dark red, because the principal coloring agent in red garnets is iron, and there is too much of it, making dark red, not light and brilliant pink.

 

[zeolite]

LD, tell us if we''re messing up your thread and we''ll get out.

TL, one of your references ... the yellow emission IS produced by 290nm +/- 20nm light, suggests short wave UV. A few minutes ago I tested with long wave UV, I just now tested with short wave UV. Still no fluorescence in 63 garnets. You must have one very special grossular.

 

[Barrett]

I have already spoken with LD offsite and she loves and would much rather her thread go this way than anything else..she appreciates the ninfo thats is shared and learned..not only as a benefit to her and to me but everyone who gets to read the info being presented..an educated consumer/collector is a deadly consumer(for the unscupulous vendors)..LOL..no green diamonds here..some great info zeolite and TL..please keep this thrwead running..it''s great for everyone

 

[T L]

Date: 4/5/2010 11:02:33 PM
Author: amethystguy
I have already spoken with LD offsite and she loves and would much rather her thread go this way than anything else..she appreciates the ninfo thats is shared and learned..not only as a benefit to her and to me but everyone who gets to read the info being presented..an educated consumer/collector is a deadly consumer(for the unscupulous vendors)..LOL..no green diamonds here..some great info zeolite and TL..please keep this thrwead running..it''s great for everyone

Well maybe we should start a new thread anyways so people will easily find it in the search engine if they''re looking for fluorescence. I think Vapid started a new thread.

Mr. Zeolite,
Thank you for your expert and scientific interpretations on these things. I know Pricescope is a consumer forum, but every once it a while, it''s nice to go off on a scientific tangent.

 

[Barrett]

hey zeo..here is a thing from elise..who told me about the cobalt bearing pakistan spinels..has to do with garnet from mexico and flours. copied and pasted

I am trying to find out more about this type of pink grossular; specifically I am looking for the high end of RI range, UV reaction and the spectrum (or any references someone can point me to). From different references including MinRec and the Garnet Lithographie issue, the Jeffrey Mine Canada and the Lake Jaco Chihuahua or Coahuila states in Mexico seem to be the sources and somewhere else in my notes, I have also the state of Morelos.

In the references above, it indicates that it is one of the few garnets which fluoresce ("scarlet red" under SW, due to the Mn). I would think that any iron would quench that effect, but it is indicated that Fe concentration is very low. Are there transparent crystals which do not have the high Ti and Fe andradite cores and are not so included? And do the transparent crystals, including those from Morelos, always fluoresce?
From what I understand, the garnets from Morelos area are the ones which are reported to be more "gemmy" and are a draw for the facetors. I just wondered if they are similar to the Sierra de las Cruces locality as far as UV and RI. They seem to have made an appearance in the gem markets under various trade names. The mineral specimens are lovely as pictured in that article and in the Garnets issue.

 

[princessplease]

Wow, that is amazingly cool!

 

[chrono]

Lots of interesting and very informative knowledge imparted by many PS members. I hope there’ll be an easy way to recall this thread for future reference since it is buried here in LD’s vanadium chrysoberyl thread. So, if I want a low iron gemstone, I need to seek East African gemstones?

 

[LD]

I love this thread - it''s so informative! As Amguy has confirmed, I have no problem with the turns this thread has taken and in fact the anorak in me is thoroughly enjoying the debate so thank you to everybody who has/is taking part. Please keep the information coming.

For those that are interested, I now have what I consider to be a definitive answer from my Alexandrite Guru, David Weinberg - if in doubt and you need to know anything about Alexandrites or Chrysoberyls, he''s the man! Anyway, this is what he told me after seeing my photos:

"If it changes color, its an alexandrite. And I am sure some alexandrites contain some vanadium but the labs don''t normally test for that and even if they do, they don''t include the chemistry on the certificate. We have tested many of the minty green (not yellowish or chartreusse) chrysoberyls and they are all vanadium chrysoberyls. But generally, alexandrite is worth more than vanadium CB but there are exceptions."

So, this is an Alexandrite (that''s possibly got Vanadium in it) with an unusual paleness to it! As TL said earlier, Alexandrites seem to find me! This is definitely a keeper now - just because of it''s interesting qualities. However, looks like I''ll have to buy a Vanadium Chrysoberyl now (for research purposes you understand

)

 

[T L]

LD,
Did David state whether it''s possible for a Vanadium chrysoberyl to be that and an alexandrite at the same time? If it does contain vanadium, it is a vanadium chrysoberyl also, or so you would think.

 

[Arcadian]

I''ve been watching this thread with a lot of interest. LD, as usual lovely stone!


-A

 

[T L]

This article states that the two chromophores (coloring agents) of alexandrite are vanadium and chromium.

http://gemologyproject.com/wiki/index.php?title=Alexandrite

 

[LD]

Apologies for the delay in reply but it got quite late here in the UK and I was desperate for bed!

Okay, more info from David ............. it''s his belief that a good many Alex contain Vanadium but even though stones may be tested by a lab, they never put the chemical composition on reports so it''s difficult to be precise how many do and how many don''t. So, l(and this is my assumption) ooking at it from a different point of view, if a Vendor believed this to be a Vanadium Chrysoberyl and had it tested to see if it contained Vanadium, the answer would come back "yes" but it wouldn''t necessarily be noted as an Alex.

However, David also told me this:-

1. If there''s a distinct colour change and there is a sign of red/pink then it''s an Alex.
2. There are certain Alex that are only found in Africa that have this colourway (and mine is from Africa)

AJS just said that they were sure it was a Vanadium Chrysoberyl and said that if I wanted to send it to a lab to be tested I could (and if it didn''t contain vanadium I could return it) or I could just simply return it. I''m not going to do either as this is a real "out of the norm" stone so I''m happy to keep it but am now on the hunt for a "proper" Vanadium Chrysoberyl!!! The one I had my eye on was sold yesterday so I''m back to the drawing board!

 

[VapidLapid]

So it''s a vanadium bearing alexandrite chrysoberyl, it''s two, two, two stones in one!
I think you lucked out and got the best of the bunch. Sorry to hear the other one you had your eye on sold yesterday. If it''s the one I bought yesterday and you want we can trade after it arrives.

 

[jstarfireb]

What a cool stone! Great info too - I''m learning a lot from this thread.

 

[brandy_z28]

That is insanely cool LD!

Gorgeous stone!

What are you going to do with it?