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 Post subject: Re: Let's talk antiquarian gem books?
PostPosted: Fri Sep 11, 2015 4:21 pm 
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Single refraction doesn't match with taaffeite.


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 Post subject: Re: Let's talk antiquarian gem books?
PostPosted: Fri Sep 11, 2015 6:19 pm 
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Isi wrote:
Single refraction doesn't match with taaffeite.

Alas, in my quick reading I misread 'single' as 'double' (I am sleep deprived).
I suppose the more likely solution is that their topaz wasn't topaz.

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 Post subject: Re: Let's talk antiquarian gem books?
PostPosted: Sat Sep 12, 2015 5:29 am 
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Yes I think that is the best option !


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 Post subject: Re: Let's talk antiquarian gem books?
PostPosted: Sat Sep 12, 2015 12:34 pm 
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Isi wrote:
Single refraction doesn't match with taaffeite.


RI ( 1,76 ) too...

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 Post subject: Re: Let's talk antiquarian gem books?
PostPosted: Sat Sep 12, 2015 2:08 pm 
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Marlow wrote:
Isi wrote:
Single refraction doesn't match with taaffeite.


RI ( 1,76 ) too...

Taafeite's RI ranges from 1.722-1.777, so that should be kosher.

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 Post subject: Re: Let's talk antiquarian gem books?
PostPosted: Sat Sep 12, 2015 5:12 pm 
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Stephen Challener wrote:
Marlow wrote:
Isi wrote:
Single refraction doesn't match with taaffeite.


RI ( 1,76 ) too...

Taafeite's RI ranges from 1.722-1.777, so that should be kosher.

Don't you use your refractometer to detect DR?


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 Post subject: Re: Let's talk antiquarian gem books?
PostPosted: Sun Sep 13, 2015 4:07 am 
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Stephen Challener wrote:
Marlow wrote:
Isi wrote:
Single refraction doesn't match with taaffeite.


RI ( 1,76 ) too...


Taafeite's RI ranges from 1.722-1.777, so that should be kosher.


You got this from Mindat? But this is wrong imo.

http://www.mindat.org/min-3863.html

I collect Taaffeite - all my eight Taaffeites ( Sri Lanka and Burma)
have with a lower RI then 1,722.

- Sri Lanka 0,74 ct dark greyish purple ( 1,718 - 1,722)
- Sri Lanka 0,53 ct medium grey bluish purple ( 1,711 - 1,715)
- Burma (0,05 - 0,41 ct ) all around 1,717-1,720
they show a medium pink fluor using LW UV - the stones a faint pink ( maybe a small chrome content?)

With a higher Zinc* or Chrome content you will have a higher RI but not 1,777.

* Spinel--> Gahnospinel --> Gahnit = increasing RI too

http://www.gia.edu/cs/Satellite?blobcol ... inary=true

http://www.ssef.ch/uploads/media/1998_K ... ravite.pdf

http://www.gia.edu/gia-gem-project-various-gems-t-z

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 Post subject: Re: Let's talk antiquarian gem books?
PostPosted: Sun Sep 13, 2015 1:02 pm 
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I think the topic is moving away from antiquarian books.....our train is getting derailed.
Image

If someone wants to start a Taaffeite thread, I'll move over the posts that would be better suited there than here....hint hint.


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 Post subject: Re: Let's talk antiquarian gem books?
PostPosted: Fri Mar 11, 2016 6:00 am 
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My hobby or passion is collecting antique jewellery and i would to more know covering this beautiful collection. :lol:


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