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 Post subject: Chrysoberyls?
PostPosted: Sun Sep 19, 2010 4:41 pm 
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Hi there! This is only my second post, so I hope you'll be patient with me.

I purchased a large lot of gemstones, including this group of six 4.5mm stones labeled chrysoberyls. Just looking at them, I had no reason to doubt this.

However, there are some things that don't quite seem right. I can't read any birefringence on the refractometer, and the polariscope and dichroscope also seem to indicate that they are singly refractive.
There is no fluorescence, and a very slight pinking under the chelsea filter.
Sadly I don't have the means to accurately measure the density.
There are surface-reaching fissures in all stones, and a few fingerprint-like inclusions in two of them.
The RI's across the six stones range from 1.768 to 1.773. Is this some odd mixed-species garnet?

Any assistance would be great!

(P.S. Please see my other post about a "tourmaline" purchased in the same lot.)


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Chrysoberyl mystery 01.jpg
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 Post subject: Re: Chrysoberyls?
PostPosted: Sun Sep 19, 2010 6:46 pm 
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You have a polariscope ... do you have an optic figure sphere? If so, look for the optic character. Chrysoberyl is biaxial positive.

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 Post subject: Re: Chrysoberyls?
PostPosted: Sun Sep 19, 2010 8:55 pm 
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Location: PNW
Mali Garnet (Also called "grandite garnet) which is a mix if grossularite and andradite typically has an RI in the 1.76-1.77 range. It is often a golden yellow to greenish-yellow color, very much like chrysoberyl and is singly refractive. It can also be brown or yellow-green. The inclusions look similar to the photos you've posted. Chrysoberyl commonly has fine silky needle inclusions, but other inclusions are possible.

My guess is that they are Mali Garnets.


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