New Mineral Named After GIA’s John Koivula
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 Post subject: Kyanite inclusions
PostPosted: Tue May 12, 2015 9:18 am 
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Hi everyone.
I have recently bought several kyanite stones (1 carat per each gem).
They are blue, sparkling. I took some pics of the inclusions under the microscope (x100).
Here one of the gems
Image
Under magnification I saw several parallel needles, I guess rutile inclusions (?)
Image
Image
Then I found this solid object, maybe a guest crystal (?)
Image

What do you think about these inclusions?
Thank you in advance
:D

ciao
Luca


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 Post subject: Re: Kyanite inclusions
PostPosted: Tue May 12, 2015 12:25 pm 
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The needles appear to be rutile.
The larger inclusion is impossible for me to ID from the picture.
GemInterest.com has a large inclusion identified as staurolite on their site, but it does not really look similar to your shot.


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 Post subject: Re: Kyanite inclusions
PostPosted: Tue May 12, 2015 2:19 pm 
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I think chances may be better that the needles are sillimanite.

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 Post subject: Re: Kyanite inclusions
PostPosted: Tue May 12, 2015 2:27 pm 
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Rutile is listed as a common inclusion in kyanite.
Sillimanite is a polymorph of kyanite.....same comp, different conditions of crystalization.
Please explain your thoughts Scar.
Not disputing, just unclear. :D


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 Post subject: Re: Kyanite inclusions
PostPosted: Tue May 12, 2015 3:45 pm 
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It's not too uncommon for any of the aluminosilicates to have taken multiple forms over their lifetimes, since their P/T conditions all fall within normal metamorphic ranges (hence why geologists love them so much--geobarometers are hard to come by.) So the chances of having some left over or some sort of pseudomorphing seem decent. Nothing profound or, if I'm honest, particularly informed, just a guess based on what I've seen in other samples and on how fibrous sillimanite usually is.

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 Post subject: Re: Kyanite inclusions
PostPosted: Wed May 13, 2015 4:10 am 
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Thank you for your valuable considerations!
I supposed the needles were rutile, since I consulted Geminterest.
However, I found that the Scarodactyl's hypothesis is very intriguing...
Regarding the 2nd crystal, I guess it's difficult to identify. I should observe it from different angles and in different conditions of light...
:D


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 Post subject: Re: Kyanite inclusions
PostPosted: Wed May 13, 2015 10:36 am 
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Random neural firing: You know how it used to be thought that black inclusions in diamonds were carbon? Now we know that is incorrect because if the inclusions were carbon they would have altered to diamond during the xlization.
I suspect the same with sillilmanite inclusions in kyanite.


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 Post subject: Re: Kyanite inclusions
PostPosted: Thu May 14, 2015 3:34 am 
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Maybe a stupid question - what about "growth tubes" ??

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 Post subject: Re: Kyanite inclusions
PostPosted: Sat May 16, 2015 10:17 am 
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Thank you for your suggestion, Marlow!
I am new to gemology. However, I though that growth tubes were typical for tourmaline and aquamarine...
But my knowledge is still very limited.
Ciao!
:D


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 Post subject: Re: Kyanite inclusions
PostPosted: Sat May 16, 2015 11:47 am 
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http://www.gia.edu/cs/Satellite?blobcol ... inary=true

Page 6

https://s3.amazonaws.com/gubelin/kyanite-34742.pdf

The wonderful Dr. Gübelin collection!!

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 Post subject: Re: Kyanite inclusions
PostPosted: Sun May 17, 2015 5:25 am 
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Your links are really valuable, Marlow!
Thank you so much
Grazie!
=D>


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 Post subject: Re: Kyanite inclusions
PostPosted: Sun May 17, 2015 8:09 pm 
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Agreed. Thanks Marlow. I think you are spot on.


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