Color shifting chrysoberyl or alex?

[T L]

I think this is a color shifting chrysoberyl, but AIGS said it was an alex. No offense to Jeff, as he's only putting out a lab report that has this information. I think these brown to yellow stones are chrysoberyls, and should not be alexandrite.

If it were a chrysoberyl, it would be worth far far less money as brownish chrysoberyl is far from the trade ideal for that stone.

http://www.ebay.com/itm/AIGS-CERTIFIED-7-1MM-COLOR-CHANGE-ALEXANDRITE-CEYLON-1-43CT-WATCH-VIDEO-/370667749021?pt=LH_DefaultDomain_0&hash=item564d84fe9d

Anyone want to comment on it?

 

[Marlow]

If this is an Alex a light pink sapphire is a ruby.

There is another round one the site - you are right to call them color SHIFT chrysoberyl - absolutely overpriced and the certificate is a joke. The same with the two stone from Madagascar - green chrysoberyl - neither V- Chrysoberyl nor Alex. A "Change" from grayish green to gray.

 

[PrecisionGem]

My understand of color change vs color shift is how far a stone's color moves on the color wheel. It it goes just one or two places, then it is a color shift. A true color change goes half way or near half way around the color wheel.

Most every stone has some amount of color shift.

 

[T L]

Well, based on the comments here, I think my biggest issue is with AIGS, they should know better. The gem brief does say "natural alexandrite."

 

[eastjavaman]

I was going to say that looks like an alexandrite, but with "light" "weak" color change, but as I see the video more, I am starting to think that it is color shifting as opposed to change.
This one is stronger version and certified by.......AIGS
http://wildfishgems.com/inc/sdetail/11090/13350

 

[Marlow]

by eastjavaman » 15 Jun 2014 23:54
I was going to say that looks like an alexandrite, but with "light" "weak" color change, but as I see the video more, I am starting to think that it is color shifting as opposed to change.
This one is stronger version and certified by.......AIGS
http://wildfishgems.com/inc/sdetail/11090/13350



No Alex in my opinion and the price....

 

[LD]

The key here is to stand back and say "what is the difference between Chrysoberyl and Alexandrite?".

To be classified as an Alexandrite, a stone MUST colour "change" from green to purple/red (or at least reddish brown) and must have a strength of change i.e. very very very weak changes may not show the colour in the incandescent colourway so may not be an Alexandrite. So the difference between Alexandrite and Chrysoberyl is where the change occurs on the colour wheel.

You do have colour "shifting" Chrysoberyls, which shift from adjacent colours on the colour wheel or within a few spaces on the wheel but do NOT change to the opposite side of the wheel. Typically shifting Chrysoberyls will never show any red or purple. So these would be Chrysoberyls.

In this case AIGS have said the colour difference is from green to brown. On that description alone you'd have to ask why this is classified as an Alex? In my opinion, this is a shifting Chrysoberyl and does not have the properties to call it a colour changing Alexandrite. I wonder though if the orange you see in the incandescent colourway is more red in real life (I doubt it because there's NO mention of this). I would still be uncomfortable classifying this as an Alex though.

Having said that ............. I've seen many stones like this being classed (in my view erroneously) as Alexandrites when they should be Chrysoberyls. It's a fine line unfortunately.

Just as an aside ............ I don't know if you remember but I once bought a Vanadium Chrysoberyl which to my great surprise was an apple green in daylight but in incandescent turned a silvery pink. I was confused because this had the colour changing properties of an Alex (albeit weak change in the incandescent colour way). I spoke with David Weinburg about this and he confirmed that as it showed pink it would probably be an Alex and probably contained a higher proportion of Vanadium than other "normal" Alex. Even with this stone, the weak colour change may actually tip it into being classified as a Chrysoberyl.

 

[Marlow]

@LD

I remember your V-Chryso/ Alex very well!!! Very interesting!!

Is there any chance to reach you via E-Mail?

Dr. Karl Schmetzer published an artikel in Journal of Gemology last winter. I loaned him 5 V- Chrysoberyland several other Chrysoberyl.

What we like - for example Kismet V-Chrysoberyl - bluishgreen mint Chrysoberyl needs:

- a V > Cr ratio ( my best is 7 : 1 = 0,07% V and only 0,01% Cr)
- a VERY low iron content ( my best has 0,21% - that is low - not the quantity - the quality is important)

Your stone is in my opinion a borderline V-Chryso / Alex - the combination of V and Cr produces a mint green daylight color but the
incandescent color is course a higherchrome content pinkish. And low Iron - that courses the flour.

I would send you a copy of this artikel.

 

[LD]

Hi Marlow

Unfortunately we don't post emails or have a PM facility on PS. However, I'm on another geology website where you can PM!

 

[Marlow]

Perfect!!

 

[eastjavaman]

LD/Marlow
what do you think of this one? is GRS good correct in their opinion? cause the video leaves me with a lot of question marks, thanks for your input.

http://www.ajsgem.com/chrysoberyl/alexandrite/alexandrite-cats-eye-7.08-carats.html

 

[Marlow]

@ eastjavaman

Me too!! Would like to discuss this with GRS. My problem is the price (again) .

 

[T L]

LD,
Maybe you have a "vanadium alexandrite."

Thank you for the detailed and informative response.

 

[Marlow]

by TL » June 16th, 2014, 2:04 pm
LD,
Maybe you have a "vanadium alexandrite."

Thank you for the detailed and informative response.

------------------

A new variety!!!!! Sensationell!!!!!

So we need a certificate!!! Then we sell it - 20.000 pct?? Not enough???? Let us ask the experts for overpriced natural untreated gems!!

Which name - MINT ALEXANDRITE - Orign Russia course we get more money....

 

[LD]

LD/Marlow
what do you think of this one? is GRS good correct in their opinion? cause the video leaves me with a lot of question marks, thanks for your input.

http://www.ajsgem.com/chrysoberyl/alexandrite/alexandrite-cats-eye-7.08-carats.html

Now then, this one I would call an Alex for several reasons (1) on the GRS report, the incandescent colourway is listed as red and certainly in the still photos on the lab report it does look a reddish brown - so you do have a jump across the colour wheel and (2) the video is very odd. It looks like it has been taken using daylight bulbs or in strong daylight but then a pen torch is used on top of that to show the incandescent colour. If I'm right, the competing light sources mean that the incandescent colourway doesn't show as it should. It would have been better to have used two completely different light sources.

So, IF the photos on the lab report and the matching description are accurate (and the variable is the video), this is most certainly an Alex.

 

[LD]

LD,
Maybe you have a "vanadium alexandrite."

Thank you for the detailed and informative response.

Unfortunately my information is that vanadium in small quantities is often found in Alex so mine is only odd because it has a mega dose! lol

 

[Marlow]

@LD

Is your stone like this one?

http://www.multicolour.com/detail/?/details/alexandrite/yax712aa/&1244716636

 

[LD]

Not really. It's much more minty green and pink in the incandescent change.

 

[Marlow]

I don't understand this stone. Low iron - o.k.

But the color is so light - would be interesting to see how many V and Cr and the ratio. Is it o.k if I send this pic to Dr. Schmetzer?

 

[eastjavaman]

(2) the video is very odd. It looks like it has been taken using daylight bulbs or in strong daylight but then a pen torch is used on top of that to show the incandescent colour. If I'm right, the competing light sources mean that the incandescent colourway doesn't show as it should. It would have been better to have used two completely different light sources.
So, IF the photos on the lab report and the matching description are accurate (and the variable is the video), this is most certainly an Alex.

Great insight LD, now watching the video again, it does seem that those 2 lights are indeed interfering with each other.

 

[LD]

I don't understand this stone. Low iron - o.k.

But the color is so light - would be interesting to see how many V and Cr and the ratio. Is it o.k if I send this pic to Dr. Schmetzer?

Yes no problem. Apparently these minty green Alex have been found in Africa but they're not the "norm". This was sold as a vanadium chrysoberyl and it was only because of the colour change that I sat back and wondered exactly what it was

Aaaaaah one thing I completely forgot to mention! If an Alex has fluorescence then it's definitely an Alex as Chrysoberyl doesn't and this is a determining factor used by labs.

 

[T L]

Aaaaaah one thing I completely forgot to mention! If an Alex has fluorescence then it's definitely an Alex as Chrysoberyl doesn't and this is a determining factor used by labs.

What if its vanadium chrysoberyl though?

 

[LD]

Aaaaaah one thing I completely forgot to mention! If an Alex has fluorescence then it's definitely an Alex as Chrysoberyl doesn't and this is a determining factor used by labs.

What if its vanadium chrysoberyl though?

Interesting question. I don't know the answer but presumably if it didn't fluoresce it'd be chrysoberyl.

 

[Marlow]

Color in daylight says V- Chryso but incandescent light and LWUV Alexandrite - my six Vanadium Chrysoberyl don't react on LWUV and Chelsea Filter.

In my opinion yourstone is an Alex with low iron but I don't understand the good colorchange with these pastell color.

 

[LD]

Color in daylight says V- Chryso but incandescent light and LWUV Alexandrite - my six Vanadium Chrysoberyl don't react on LWUV and Chelsea Filter.

In my opinion yourstone is an Alex with low iron but I don't understand the good colorchange with these pastell color.

Yes, although I bought it as a Vanadium Chryso the colour change and fluor indicates Alex. Why are you puzzled about the colour change (which is weak by the way rather than good)? If it's Alex material (and much Alex has vanadium) and those change colour so why wouldn't this one do so???????

 

[Marlow]

@ LD

I talked to Dr. Schmetzer.

It is possible that a low Cr content produces a Color change. In his opinion judging from the pics: No V-Chrysoberyl.
My question: Do you have a refractometer and are there inclusions ( negative crystals, apatite..)
Otherwise I would send it to a Lab. There are Kyocera synthetic alexandrite, V-Chrysoberyl and PINK Chrysoberyl (Titan!).

I think it is unusual to have a color change in combination with such a light color - I' m fascinated by this gem.
Look at the Alexandrite from India - super daylight color - you expect a change like a hematita alex and nothing happens.

If puzzled is negative - no - this one is much more interessting then the 3427th cuprian oval tourmaline or another Tanzanite.
I want to understand how V, Cr and Fe work in Chrysoberyl.

 

[LD]

@ LD

I talked to Dr. Schmetzer.

It is possible that a low Cr content produces a Color change. In his opinion judging from the pics: No V-Chrysoberyl.
My question: Do you have a refractometer and are there inclusions ( negative crystals, apatite..)
Otherwise I would send it to a Lab. There are Kyocera synthetic alexandrite, V-Chrysoberyl and PINK Chrysoberyl (Titan!).

I think it is unusual to have a color change in combination with such a light color - I' m fascinated by this gem.
Look at the Alexandrite from India - super daylight color - you expect a change like a hematita alex and nothing happens.

If puzzled is negative - no - this one is much more interessting then the 3427th cuprian oval tourmaline or another Tanzanite.
I want to understand how V, Cr and Fe work in Chrysoberyl.

Marlow RI confirmed as Alex. Tested by the seller, me and an Independent. This is not a synthetic. The stone is in a bank vault so unfortunately can't loupe/microscope it. From memory it's eye clean but it's only a small stone.

David Weinberg confirmed this is an Alex and that he's seen some very similar stones.

I'm puzzled by your comment about Alex from India????? I've seen some spectacular Indian Alex (glorious daylight but also good in incandescent.

 

[Marlow]

I have seen both from India.

Top daylight color and excellent color change and anotherone with no color change. Depends on the chrome amount and the V/ Cr ratio.
Let's say you have 0,5 % Cr ( Hematita average) and 0,05 V you will have a good change - with increasing amount of vanadium still good change - the daylight color maybe more intense.

 

[chrono]

I guess it depends on which side of the table you are standing at. A vendor can certainly call it a weak colour change alexandrite and back it up with a lower tier lab report whilst the buyer has the right to call it a colour shift chrysoberyl (the same way one looks at ruby versus pink sapphire).