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 Post subject: G&G eBrief Brainteser
PostPosted: Mon Sep 05, 2011 3:41 pm 
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I clicked on the link we have on the left for G&G eBriefs and stumbled on this Brainteaser from April.

I was surprised (in an really positive way) that it incorporated Visual Optics. \:D/

Check this out:
Nite Light
What is it?
Image
Photo by Robert Weldon

And tell us why you think so.


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 Post subject: Re: G&G eBrief Brainteser
PostPosted: Mon Sep 05, 2011 3:54 pm 
Rhodonite.
Dichroic colours (diagnostic?)
High(-ish) RIs
Moderate birefringence (so not Rhodochrosite and, anyway, the colour is 'off')

Nice stone.... please may I have it :wink:


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 Post subject: Re: G&G eBrief Brainteser
PostPosted: Mon Sep 05, 2011 4:01 pm 
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Gee I'm glad this wasn't a prize winning quiz.
It would have been pretty boring.

I actually think it was the presence of cleavage which separates it from other possibilities.


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 Post subject: Re: G&G eBrief Brainteser
PostPosted: Mon Sep 05, 2011 4:02 pm 
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Rhodonite? It might also be Rhodochrosite...? I've seen Rhodo's that color.

High RI, moderate birefringence , brownish-red pleochroism, typically showing cleavage planes inside of stone.


Just a slightly educated guess from a new GIA student!

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 Post subject: Re: G&G eBrief Brainteser
PostPosted: Mon Sep 05, 2011 4:15 pm 
Stonebender wrote:
Rhodonite? It might also be Rhodochrosite...? I've seen Rhodo's that color.

High RI, moderate birefringence , brownish-red pleochroism, typically showing cleavage planes inside of stone.


Just a slightly educated guess from a new GIA student!


Well, my references give a very large biref and, working on memory of the small number of each I've actually *viewed* the colour split under the dichroscope is right for Rhodonite but not Rhodochrosite. Others who have seen more may feel differently. But it's the biref that's the Rhodochrosite 'killer' I think.


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 Post subject: Re: G&G eBrief Brainteser
PostPosted: Mon Sep 05, 2011 4:17 pm 
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Refractive Index of rhodochrosite is moderate:
1.680-1880
Birefringence is quite high: 0.020
But, indeed, it DOES occur in that color and has perfect cleavage.

BUT, RI and Birefringence knock it out of the competition.


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 Post subject: Re: G&G eBrief Brainteser
PostPosted: Mon Sep 05, 2011 4:20 pm 
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Kerensky wrote:
Stonebender wrote:
Rhodonite? It might also be Rhodochrosite...? I've seen Rhodo's that color.

High RI, moderate birefringence , brownish-red pleochroism, typically showing cleavage planes inside of stone.


Just a slightly educated guess from a new GIA student!


Well, my references give a very large biref and, working on memory of the small number of each I've actually *viewed* the colour split under the dichroscope is right for Rhodonite but not Rhodochrosite. Others who have seen more may feel differently. But it's the biref that's the Rhodochrosite 'killer' I think.


Hmm, I KNOW you knock me out of the park when it comes to this stuff, but I have to say my guess wasn't too bad for an amateur working from memory. :)

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 Post subject: Re: G&G eBrief Brainteser
PostPosted: Mon Sep 05, 2011 4:30 pm 
Trust me.... it's me that's the amateur :lol:


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 Post subject: Re: G&G eBrief Brainteser
PostPosted: Mon Sep 05, 2011 4:57 pm 
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Wanna do another?
Here is the link to the G&G Brief page
Here is a copy of that page:
Image

I hope you are all reading these briefs when they become available.
They are an excellent source for cutting edge Gem News.


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 Post subject: Re: G&G eBrief Brainteser
PostPosted: Mon Sep 05, 2011 4:59 pm 
Moldavite? Czech it out :lol:


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 Post subject: Re: G&G eBrief Brainteser
PostPosted: Mon Sep 05, 2011 5:01 pm 
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Looks like gas bubbles. Isotropic. Czech republic. Could it be moldavite?

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 Post subject: Re: G&G eBrief Brainteser
PostPosted: Mon Sep 05, 2011 9:12 pm 
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oh welll a little late with my guess ... but yes moldavite ...

George

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 Post subject: Re: G&G eBrief Brainteser
PostPosted: Tue Sep 06, 2011 12:49 am 
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here is another one
http://app.e2ma.net/campaign/1401417.26 ... rainteaser

Name That Inclusion!
Attachment:
e1254776416.jpg
e1254776416.jpg [ 42.2 KiB | Viewed 3336 times ]

Nature has fashioned an image in this diamond better than any laser could. What is this inclusion?

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 Post subject: Re: G&G eBrief Brainteser
PostPosted: Tue Sep 06, 2011 3:55 am 
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Some sort of radiation stain?

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 Post subject: Re: G&G eBrief Brainteser
PostPosted: Tue Sep 06, 2011 5:43 am 
Hmmm.... if it's an inclusion it beats me. My guess is that it is an artefact - an optical illusion, if you prefer. But, if that is so, I don't know what it is that is being multiple-reflected.


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