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 Post subject: lab alexandrite
PostPosted: Tue Dec 29, 2009 11:25 pm 
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Okay, nobody responded to my other post, so I'll post another one. I ordered a lab alexandrite. In the plastic baggie, it started out a nice aquaish blue. But when I took it out of the baggie, and took it out into the sun, it gradually faded into an ordinary amethyst purple. Yes, it was more bluish in sunlight, and more red in incandesant and candlelight.
Has anyone else ordered a lab grown alexandrite and notice that it is initially a lighter blue and changes to a purple?


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PostPosted: Wed Dec 30, 2009 1:25 am 
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Hi and welcome to the forum.

I need a little clarification.

You ordered a synthetic alexandrite or a lab-grown imitation alexandrite?

Was the fading permanent or does it appear different shades when viewed using different light sources?


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PostPosted: Wed Dec 30, 2009 4:40 am 
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I bought a "synthetic alexandrite" from fleabay some time ago just to see what it was like, and it turned out to be just a light reddish purple, no color change or shift. I haven't bothered to test it, but I strongly suspect it is just glass.

There are a number of color change synthetics, including corundum, cubic zirconia, and synthetic chrysoberyl (alexandrite.) The corundum and CZ can be made with a variety of color change effects, but the interesting one to me is the synthetic alexandrite. Unfortunately, based on pictures I have seen, the synthetic alexandrite actually appears to change between blue and purplish red.

What I want is that nice emerald green to red change, but I have only seen that in a couple of natural alexandrites and one color change garnet that I have.

I cannot guess from the info available what Ilikagems has, but the color change described would be consistent with any of the color change synthetics, as far as I can tell.

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PostPosted: Wed Dec 30, 2009 11:30 am 
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The best color change I've seen with natural alex is bluish green to raspberry red.


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PostPosted: Wed Dec 30, 2009 1:23 pm 
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I've never seen a green to red alex color change. I asked josh at pala why that was. He said in the "old days" they jewelers would use a phosphorus match to illuminate the stone, thus skewing the color spectrum. I can't recall if that made it more red or more green..(I'm thinking green). In any case, even the AGTA tucson show alexandrites were more of a teal green than an emerald green. The only red to green colorshift i've heard about has been on a vanadium sapphire, in indirect south facing 3pm winter texas light.

The one man made alexandrite I have really is a synthetic chrysoberyl and does have the red -> teal green cc.

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PostPosted: Wed Dec 30, 2009 4:36 pm 
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I sent the stone to someone and don't have it. It was advertised as russian sp? Chrochorski method synthetic alexandrite.
It didn't claim to have the green to red shift but a blue to red shift-in daylight vs incandecent-which it did slightly. What I'm mainly asking about is when I first got it, it was an aquaish blue-and then upon exposure to sunlight? air? that color disapeared and it settled into a bluish purple-to purple reddish color shift. Under different lighting sources-could not get the original blue to appear as it was originally in packaging, and about-say 5-7 minutes after taking out of packaging.
Maybe nobody else has noticed it, as they got one after that fading affect had already occured. Maybe I can find the listing info to post.
The aqua blue component of the color permenantly fading and disappearing- different from the color shift under lighting conditions-ya know?


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PostPosted: Thu Dec 31, 2009 4:35 am 
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hi,

ilikagems wrote:
Chrochorski method synthetic alexandrite.?


peraphs you're talking about Czochralski pulling method
ciao
alberto

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 Post subject: check its RI
PostPosted: Wed Jan 27, 2010 3:27 pm 
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Dear friend

Check the RI of the stone. It should be new synthetic color change sapphire. which have three types shads and pinkish in blub (candle) light.


with best regard!

HUK


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PostPosted: Wed Jan 27, 2010 8:22 pm 
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In my handy little brochure for synthetics I can get
Alexandrium H. 6.75 RI 1.51 this is pink with colour change

Corundum Alexandrite (Swiss grown) H 9 RI 1.76 hmm doesn't mention the colours

Alexandrite H 8.5 RI 1.74
This is a true syn Alex with strong colour change.
The first 2 are worth cents per carat.
The last one :shock: Your paying big dollars per carat.
Steve if you want me to ask further about this just pm me. The last one is available in 4 to 10 carat pieces.

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PostPosted: Thu Apr 01, 2010 10:06 pm 
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ilikagems wrote:
I sent the stone to someone and don't have it. It was advertised as russian sp? Chrochorski method synthetic alexandrite.
It didn't claim to have the green to red shift but a blue to red shift-in daylight vs incandecent-which it did slightly. What I'm mainly asking about is when I first got it, it was an aquaish blue-and then upon exposure to sunlight? air? that color disapeared and it settled into a bluish purple-to purple reddish color shift. Under different lighting sources-could not get the original blue to appear as it was originally in packaging, and about-say 5-7 minutes after taking out of packaging.
Maybe nobody else has noticed it, as they got one after that fading affect had already occured. Maybe I can find the listing info to post.
The aqua blue component of the color permenantly fading and disappearing- different from the color shift under lighting conditions-ya know?


I observed exactly the same effect in a fake alexandrite brought from Laos. Although it took me several years to notice it because of limited exposure to the sun. In fact, I ascribed it to the time. The alexandrite I have shows strong fluorescence, so I assume it is synthetic spinel. I have a set of three stones, from the same source, and all of them show the same effect. When they were bought, they showed strong color shift from dark purple in incandescent light to light blue in the sun, but as time goes by, the effect is gradually disappearing. Now I do not even see any blue, although the stones exhibit a shift from dark purple to violet. They are beautiful and much brighter that amethysts though.


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PostPosted: Fri Apr 02, 2010 1:54 pm 
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gemsevermore wrote:
What I want is that nice emerald green to red change, but I have only seen that in a couple of natural alexandrites and one color change garnet that I have.

If don't mind a synthetic, why not check out Tourmalike. It is a synthetic type of laser glass, has the nice emerald/tourmaline green to red/pink color change. Closest thing I have found to what the old top end natural alexandrite looked like. Makes an amazing stone if custom cut too!


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PostPosted: Fri Apr 02, 2010 2:36 pm 
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I've collected natural Alexandrites for over 20 years and have them from all localities. A high quality natural Alex will be, typically, a forest green in daylight changing to an Amethyst purple with some flashes of red in incandescent lighting.

I was once sold a synthetic as "natural". It looked too good to be true which caused alarm bells. It was exactly the colour way it should be and the change was dramatic. However, it turned out, after testing, to be synthetic. Synthetics can have the same change as a natural Alex or they can have the reverse colour change (so you'll see red in daylight and green in incandescent). I've also seen some that look very blue and then change to purple etc etc.

I would think that the change you observed initially was a result of the lighting you were viewing the gemstone in. In certain lights you will get a mix of both colours and perhaps this is what happened?


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PostPosted: Fri Apr 02, 2010 4:51 pm 
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Here is an Alex that was "Stone of the Day" a long time ago. I did not keep record of carat weight back then or vendor, but I'm 95% it's from www.multicolour.com & is Orissa, India orgin.

Image

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 Post subject: More information please on reverse color change
PostPosted: Sun Apr 04, 2010 3:32 pm 
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Hi LovingDiamonds,

Do you have a sample of the reverse Alexandrite effect synthetic gemstone? Do you have any information on it?

I have been working with a variety of cuprian Elbaite (I call Laurellite) that demonstrates a reverse Alexandrite effect color change. It goes from blue green in incandescent light to purple in daylight.

When the GIA and an expert that I hired to investigate Laurellite reported on it a few years ago, they did not know of any other gemstone/substance, natural or synthetic, that demonstrates the reverse Alexandrite color change.

A sample of the synthetic reverse Alexandrite effect gemstone should be tested by a qualified gem lab for the sake of science.

Bruce


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PostPosted: Mon Apr 05, 2010 12:01 pm 
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Hi Bruce - I'm sorry but the reverse colour change wasn't actually my stone. A friend of mine had bought it in a ring from an antique shop and was told it was an Alex. She showed it to me and I knew instantly it wasn't. I don't know if she still has it or not but I'll ask.

I've only seen 3 stones like this and the others were posted on other forums - interestingly they were also in antique/aged rings and had been sold as Alexandrite.

Czochralski Alexandrite tends to have the same colour change you've observed in your Cuprian Elbaites. They are a blue changing to purple/red (and not much green at all).


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