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 Post subject: Amethyst Natural?
PostPosted: Wed Nov 02, 2016 6:53 am 
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Hi, and this is my second question.

I have two Amethysts set in Jewlerry. By looking carefully I found that the facettes and the whole Stone Looks different to other Amethysts I have seen before.
-Lots of smudges. On the outer Stone and also inside the Stone
-The facetts are not sharp. They are very smooth. It Looks like as if the Piece was molded/casted

The refractometer tells me it should be a Amethyst.

Could these stones be syntethic? Thank you Mike


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 Post subject: Re: Amethyst Natural?
PostPosted: Wed Nov 02, 2016 5:24 pm 
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From the GIA's Gems and Gemology:
Click the link below to download the pdf.
A SIMPLE PROCEDURE TO SEPARATE NATURAL FROM SYNTHETIC AMETHYST ON THE BASIS OF TWINNING

and:
[pdfview]http://epubl.ltu.se/1404-5494/2008/021/LTU-HIP-EX-08021-SE.pdf[/pdfview]


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 Post subject: Re: Amethyst Natural?
PostPosted: Wed Nov 02, 2016 6:05 pm 
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Just in broad strokes, rounded facets are never indicative of a synthetic. You can't cast a synthetic that way--they are grown as boules or crystals and have to be faceted like any other stones. Glass can be cast but identification is trivial on other factors.
I'm not sure what you mean by "Smudges" though. Color zoning is typical of natural amethyst and less so of synthetic amethyst--no doubt it could be done, as we've seen in synthetic ametrine, but the types of zoning produced are clearly limited.
Edit: by the way, the above thesis is a real delight. The grammar may not be the best but it is a very sparse, direct presentation of some interesting systematically collected data.

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 Post subject: Re: Amethyst Natural?
PostPosted: Wed Nov 02, 2016 9:40 pm 
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Stephen Challener wrote:
Edit: by the way, the above thesis is a real delight. The grammar may not be the best but it is a very sparse, direct presentation of some interesting systematically collected data.


I really think this thesis was a great find. Lots of really useful info and :oops: I didn't notice any grammar issues.


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 Post subject: Re: Amethyst Natural?
PostPosted: Thu Nov 03, 2016 1:58 am 
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It looks as though they have gone straight from a bit of a coarse lap to the polish, leaving lots of scratches, the edges of which have been smoothed by the polish.


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 Post subject: Re: Amethyst Natural?
PostPosted: Thu Nov 03, 2016 2:18 am 
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i see round facets and orange peel on the surface. might be just moulded glass. Topic starter please check for birifrigence using refractometer and polaricope. Sorry for my English

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 Post subject: Re: Amethyst Natural?
PostPosted: Thu Nov 03, 2016 2:19 am 
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The clue is if its single refractive or doubly refractive

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 Post subject: Re: Amethyst Natural?
PostPosted: Thu Nov 03, 2016 11:19 am 
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looks like glass to me.


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 Post subject: Re: Amethyst Natural?
PostPosted: Thu Nov 03, 2016 1:43 pm 
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Hi Barbra, thank you very much for the PDF Link on distinguishing the genuine pieces from the synthetics. Very valuable. I will check on Monday again with the polariskop for twinned brazilian marks. To @ the other members who cometed. Thank you. Afterall it might only be molded glass, as it does look to have very soft facettes. Will also test again with the refractometer.. rgds Mike


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 Post subject: Re: Amethyst Natural?
PostPosted: Thu Nov 03, 2016 3:26 pm 
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Touch it with your tougue.


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 Post subject: Re: Amethyst Natural?
PostPosted: Thu Nov 03, 2016 3:42 pm 
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yes as Bill Hanneman said, if its warm or cold?

becouse of ammorphus structure of glass it feels warm to the touch. but wash you stone well first from RI i=liquid (its poisoness)

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 Post subject: Re: Amethyst Natural?
PostPosted: Thu Nov 03, 2016 3:44 pm 
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Twinned crystal test is not reliable for synthetic/natural origine. They leard how to grow twinned quartz synthetics about 20 years ago and still grow it sometimes

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 Post subject: Re: Amethyst Natural?
PostPosted: Wed Nov 09, 2016 4:47 am 
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Hi, thanks again for the Infos. When tested on the lip it is cold. I found the Bulls eye yesterday ;))))


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 Post subject: Re: Amethyst Natural?
PostPosted: Wed Nov 09, 2016 5:19 pm 
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Cool...but we still don't know if it is natural of synthetic.
Twinning should not be dismissed.
Just because something CAN be done does not mean it IS being done.


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 Post subject: Re: Amethyst Natural?
PostPosted: Thu Nov 10, 2016 8:15 am 
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I would too rely on twinning, not 100%, but on the basis of strong probability.
Are ther absolutely no inclusions in this stone ?


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