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 Post subject: ALEXANDRITE OR NOT??
PostPosted: Tue Jul 21, 2009 2:48 pm 
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Location: Mumbai, India
Hello,
I have recently got a greenish yellow chrysoberyl cat's eye which when seen under incandescent light shows a color change to brownish red.The stone is from Srilanka and has a weight of 4.77cts.The color change is clearly visible without the need to roatate it in any angle.I am posting pics of the stone in daylight and incandescent light.Can this be termed as an alexandrite.Also what are the requirements for this to be termed an alexandrite and not a color changing chrysoberyl (chromium needs to be present?? etc.).Also in which lab should i certify such a stone. (GIA, GUBLEIN, GRS??)
Any help will be appreciated.
Thanks
Vismay

PICTURE:
Image

http://img24.imageshack.us/img24/8388/76315004.jpg

THE COLOR CHANGE IN STONE IS PRECISELY AS SEEN IN THE PHOTOGRAPH WITHOUT ANY FORM OF COLOR MANUPILATION.

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PostPosted: Tue Jul 21, 2009 5:25 pm 
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hi, vismay!
here's a discussion on some alexandrite with some links in the post from last week:

http://gemologyonline.com/Forum/phpBB2/ ... 1c496edba3

i've seen on the gemshopping channel alexandrite from sri lanka and tanzania. the stone pictured is a nice stone, and it looks like a color shift?? (hopefully one of our gemmo pros can clarify if it's color change or color shift) and a nice size, too. color shift stones are just as rare, though, and expensive.

i'm sure one of our members can suggest a lab to send the stone to get checked out for you and share more information with you on the sri lankan alexandrite.


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PostPosted: Tue Jul 21, 2009 11:55 pm 
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I am not positive on this, but I was always under the understanding, lol, that the yellow c/c or c/s material was simply Chrysoberyl. It can be differentiated from the spectrum, since Alexandrite is colored by chromium and chrysoberyl by iron(if memory holds), if it is Alex you should have diagnostic lines in the red/orange part of the spectrum for chromium.

The above said, I am almost positive that the yellow material, c/c or c/s, would be chrysoberyl and NOT alexandrite. The reason I am almost positive is that iron causes the yellow and brown coloring of chrysoberyl, therefore it would not be chromium causing it and so it would not be alexandrite. I was always taught that alexandrite will be your basic(fluctuating slightly in tones of course), generically speaking, green to red color change.


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PostPosted: Thu Jul 23, 2009 1:44 pm 
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Joined: Tue Apr 07, 2009 12:57 pm
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Location: Mumbai, India
Hey guys,
Thanks for your replies.I checked the specefic stone under short and long wave U.V. and the stone is showing a very weak red color...I still have to check it under chelsea color filter but it is definately red under L.W.U.V.(I put chrysoberyl cat's eye of same color along with it and checked under L.W.U.V.)Also my apologies but the color of the stone in daylight is a MUCH MORE greenish than in the picture. (I don't know but the picture seemed fine on my laptop but when i opened the site on a normal comp it is the daylight color is showing more yellowish brown than green) but the color in incandescent light is perfect as in the picture....I would also like to add that the color is absolutely grass green in one direction (when viewed along the side of the stone) and it also shows a color change to reddish brown in that direction.
ALSO
I was reading book by R. Webster (Gems, sources and description) and there is a specefic mention on srilankan alexandrites which change color from yellow green to reddish brown which is much like my stone, If someone could give me some knowledge about srilankan alexandrite cat's eye it would be really helpful.
THE said stone was graded as an alexandrite cat's eye by the GEMMOLOGICAL INSTITUTE OF INDIA.
BUT I AM NOT SATISFIED AND WANT TO LOOK INTO THE TECHNICAL DETAILS WHICH WOULD BE NEEDED TO GET IT CERTIFIED AS AN ALEXANDRITE BY BETTER LABS (GIA, GUBLEIN, GRS) ETC.
PLEASE TELL ME MORE TESTS I CAN PERFORM TO CONFIRM BEFORE SENDING IT TO SUCH A LAB AS THE CERTIFICATION IS EXPENSIVE (I AM THINKING OF GETTING A CHEMICAL ANALYSIS DONE WHICH WOULD INDICATE THE PRESENCE OF CHROMIUM)
HELP.

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PostPosted: Thu Jul 23, 2009 1:58 pm 
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I would call it an alexandrite of commercial quality.

Most of the alex that I've seen has had a color change similar to yours. I'd call it greenish bug juice to reddish bug juice.

This material is relatively inexpensive.

Most gems we see across the board are commercial quality.

That's why the few that are exceptional are expensive; they are truly rare.


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PostPosted: Fri Jul 24, 2009 12:09 am 
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Ah, didn't realize it was green. On my screen it is almost completely a subdued yellow. Sorry.


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PostPosted: Fri Jul 24, 2009 12:12 am 
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Close, Mr. Swish....I'd say it's spot on bug juice. :wink:


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