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 Post subject: Re: Weird color change/shift garnet--cc usumbara??
PostPosted: Sun Aug 09, 2020 5:54 am 
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Joined: Wed Jul 22, 2015 6:39 am
Posts: 166
gembug wrote:
I experienced the same thing with a parcel of cc garnets from Tanzania. I was confused enough to send a few pieces to Barbra to put through her Raman. They came back as pyralspite garnet - I'll have to come back here to post the link to that thread.

edit: here is the original thread:
https://www.gemologyonline.com/Forum/phpBB2/viewtopic.php?f=34&t=24343&hilit=garnet+umbasara

So to recap - the cc garnet appears green or bluish in transmitted light when viewed across the shorter dimension, and shows reddish in the same transmitted light when viewed through the long dimension. Like the tourmaline umbasara effect, but is it the same?

-Allan


Allan, thankyou for the very informative post.
Yes your recap is correct. Perhaps I jumped the gun assuming it was usumbara effect :oops:
It just looks very similar effect wise


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 Post subject: Re: Weird color change/shift garnet--cc usumbara??
PostPosted: Sun Aug 09, 2020 12:02 pm 
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Joined: Sun Oct 16, 2005 12:22 pm
Posts: 21602
Location: San Francisco
It would be my pleasure to scan a small bit.
Let me know if you decide to send me one. I'll surely send it back to you when done.


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