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 Post subject: What has caused this perfect elipse in amber cabochon?
PostPosted: Wed Apr 09, 2014 7:24 pm 
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This cabochon is part of my stone set and I presume it is amber.
Please take a look and tell me the possible causes for this perfectly formed ellipse within the cab. Its definitely not on he outside.


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 Post subject: Re: What has caused this perfect elipse in amber cabochon?
PostPosted: Thu Apr 10, 2014 8:00 am 
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Why do you presume it is amber?


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 Post subject: Re: What has caused this perfect elipse in amber cabochon?
PostPosted: Thu Apr 10, 2014 10:08 am 
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Joined: Mon Feb 11, 2008 11:11 pm
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It is not uncommon for elipseoid zones to develop in Mexican opal.

viewtopic.php?f=6&t=13215&hilit=huevo&start=0

What causes them is not known with certainty; one common speculation is that it has something to do with dehydration.

cheers,
Hans Durstling
Moncton, Canada

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 Post subject: Re: What has caused this perfect elipse in amber cabochon?
PostPosted: Thu Apr 10, 2014 6:13 pm 
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Facetnator wrote:
Why do you presume it is amber?


I say presume because I have just started in gemmology and need to guard against making definitive statements/judgements because I am still very inexperienced. [-X

I had to examine and describe this cabochon and report my findings in an observation area. First I looked at it, felt it and then made up a saline solution to see if it would float. It did float. I then looked at it under x10 loupe and found what looked like an insect leg, a seed and some other bits of dark material that could be organic matter and of course this ellipse and two other similar lines on the opposite side that looked similar but not the same elliptical shape. I didn't do a burn or heat test or apply any acid to the cabochon.

Someone else described the same specimen number to mine and described fracture lines. I'm not convinced that those very fine lines and ellipse in my specimen are fracture lines but I could be wrong.

What do you think the specimen might be? Here is a macro photo
of the whole cabochon taken by my digital camera.


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Last edited by Gem 14 on Fri Apr 11, 2014 4:33 am, edited 1 time in total.
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 Post subject: Re: What has caused this perfect elipse in amber cabochon?
PostPosted: Thu Apr 10, 2014 6:25 pm 
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Hans Durstling wrote:
It is not uncommon for elipseoid zones to develop in Mexican Opal.


Thanks for sharing the link to the opal image, its very interesting. You might well be right about dehydration causing the fine lines in my image.


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 Post subject: Re: What has caused this perfect elipse in amber cabochon?
PostPosted: Fri Apr 11, 2014 12:30 am 
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Joined: Mon Feb 11, 2008 11:11 pm
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If it floats on saline it's certainly not opal; assuming it is amber, and is a study specimen, (and this is exceedingly speculative so take it as not more than that) it could be, might be, maybe - reconstituted amber and the ellipse a suture line remaining from the melting together of two or more separate pieces. Like I say it's farfetched but it's not impossible that they might be throwing you a curve ball to test your analytical skills.

Cheers again
Hans Durstling
Moncton, Canada

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 Post subject: Re: What has caused this perfect elipse in amber cabochon?
PostPosted: Fri Apr 11, 2014 4:50 am 
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Hans Durstling wrote:
If it floats on saline it's certainly not opal. Like I say it's farfetched but it's not impossible that they might be throwing you a curve ball to test your analytical skills.


Some of the specimens in the kit are synthetics, optic glass, and a dyed example. My specimen above is listed as Amber on the list. But I agree with you, we should verify what we are told and make sure the material is what they say it is - anyone could make an error labelling something. Its likely we'll see many curved balls especially in exams.


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