New Mineral Named After GIA’s John Koivula
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 Post subject: Imitation Tanzanite
PostPosted: Wed Feb 08, 2006 1:11 pm 
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I know glass is commonly used as a Tanzanite imitation, along with synthetic fosterite. I know some people try to sell cordiertite (iolite) as tanzanite. Are there any other imitations on the market?

I had another EBay buyer come in this week with a pendant, a ring, and a pair of earrings that were sold to her as"tanzanite". Upon doing a gem identification for her, I quickly determined that none of the stones were tanzanite - but I couldn't determine the exact material.

They were all singly refractive, one of the stones showed strong ADR, so of course none of them showed pleochhroism (although two of them looked like they had some red flashes to the human eye - but not under the dicroscope). They had no inclusions that would identify them, but the thing that threw me was the RI on all of them - they were all OTL and the RI's were spread between 1.81 - 2.15 which rules out glass.

Are G.G.G., YAG, and CZ being made to look like tanzanite these days?

Of course the seller had a "no return" policy and the buyer knew just enough about gemology to be dangerous. Whenever my clients tell me they've purchased something on EBay and they want me to ID it or appraise it, I brace myself because I know I will probably have to deliver the bad news. So far every EBay purchase I have seen in my store has been misrepresented.


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PostPosted: Wed Feb 08, 2006 2:48 pm 
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Hi Sniz,

I don't know of all tanzanite imitations but CZ is at least one of them. See below.

http://www.hsn.com/cnt/prod/default.asp ... =&ocm=sekw


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PostPosted: Wed Feb 08, 2006 4:04 pm 
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Sniz! I think I have seen YAG on JTV that the show hosts were refering to as Tanzanite colored... or a tanzanite "like" color.
And other shopping channels have been selling tanzanite simulents in jewelry, not sure what material it was though.

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PostPosted: Wed Feb 08, 2006 5:03 pm 
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Neil also mentioned a Synthetic fosterite/YAG doublet a while ago in chat.


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PostPosted: Wed Mar 15, 2006 8:46 am 
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Dear snizzy,

As JB says CZ it's available as Tanzanite imitation.
I have this type of spectrum for tanzanitelike CZ:
Purplish blue CZ.
Image
Violet CZ:
Image

YAG is an other tanzanite (sometime sold as Tanavyte).
Read this litle article GIA:
http://www.gia.edu/newsroom/issue/2798/ ... ails.cfm#3

This paper says for YAG "Tanavyte":
GIA wrote:
Some manufacturers have grown a bluish purple synthetic yttrium aluminum garnet (YAG) that mimics tanzanite’s color. One version goes under the trade name Tanavyte. The material is singly refractive and over the limits of a standard refractometer, with an RI of 1.80 or higher. Because it is singly refractive there is no pleochroism, an important distinction. With the polariscope, it might show anomalous double refraction resulting from strain within the crystal :wink: .


;-)

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PostPosted: Wed Mar 15, 2006 11:32 am 
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Thanks Gemça! Great information! I am seeing more and more of these stones lately.

Do you have any info on the tsavorite colored CZ?


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PostPosted: Fri Mar 17, 2006 4:15 pm 
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Moderator wrote:
Thanks Gemça! Great information! I am seeing more and more of these stones lately.

Do you have any info on the tsavorite colored CZ?


I have recorded this spectrum:
Image
for this type of green CZ (like pale colored tsavorite).
Image
with:
d~5.64
SWUV : pale green
LWUV : inert

In other hand, I have encoutered a deep green YAG that can imitate the deep green tsavorite:
Image
fort this type of green:
Image

Note :roll: some new flux synthetic garnet like EGG
Image
can imitate tsavorite to ;-)

I hope that can help you.

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