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 Post subject: How do you call Black Color Translucent Chalcedony
PostPosted: Mon May 13, 2013 6:03 pm 
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Hello everyone,

I am a bit confused. I am identifying various black stones for the GEM ID course from GIA. How do you call Black Color Translucent Chalcedony if it does not have any white straight parallel bands of different colors. When viewed through the microscope with the darkfield illumination, i can see the edges that are dark red or brownish color. It means it is dyed but how do you call this chalcedony? still ONYX? or something else?


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 Post subject: Re: How do you call Black Color Translucent Chalcedony
PostPosted: Mon May 13, 2013 8:37 pm 
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Joined: Sun Oct 16, 2005 12:22 pm
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Location: San Francisco
I can't speak for the GIA, but I'd call it dyed chalcedony.
Why don't you ask your instructor.
Let us know what you find out.
Using the term "onyx" is a little sketchy.


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 Post subject: Re: How do you call Black Color Translucent Chalcedony
PostPosted: Wed May 15, 2013 5:58 am 
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Joined: Wed Jan 23, 2013 5:29 pm
Posts: 1047
Location: Paris
Hello
In France the word onyx applies to :
- black uniform chalcedony
or
- banded white and black agate (used for cameos for instance)
whether dyed or not.
But then, it's only in France !


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 Post subject: Re: How do you call Black Color Translucent Chalcedony
PostPosted: Wed May 15, 2013 9:49 pm 
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Joined: Sun Dec 30, 2007 12:01 am
Posts: 556
Location: Vancouver, Canada
As a trade cutter I have been presented with so many different materials that have presented as Black Onyx. Of course none of them are the Black Onyx that geologists or gemmologists agree on. Glass, plastic and everything in between including wood and coral will pass as "jewellers black onyx"

Of course none of them including the real thing are of much value anyway, this discussion is moot.


Tony.

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Beautiful British Columbia


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