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 Post subject: How to separate Manmade Glass vs Obdisian vs Moldavite
PostPosted: Mon Dec 06, 2010 1:56 am 
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Since that three igneous rock species could overlap in visual and physical characteristics, then how can we separate them? Thanks.......


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 Post subject: Re: How to separate Manmade Glass vs Obdisian vs Moldavite
PostPosted: Mon Dec 06, 2010 5:20 am 
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I would use the microscope and study internal characteristics.

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 Post subject: Re: How to separate Manmade Glass vs Obdisian vs Moldavite
PostPosted: Tue Dec 07, 2010 1:02 pm 
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Separation is difficult. RI can overlap, inclusions such as flow lines and bubbles can be encountered in moldavite as well as artificial glass. "Undulating regions of snake-like schileren and gas bubbles in Czech moldavite creat a characteristic pattern for this material"; so says the Photo atlas 1986 page 286. Good luck, especially when the material is faceted.


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 Post subject: Re: How to separate Manmade Glass vs Obdisian vs Moldavite
PostPosted: Tue Dec 07, 2010 1:14 pm 
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Quote:
Since that three igneous rock species could overlap in visual and physical characteristics, then how can we separate them? Thanks.......



Million dollar :?: [-o< [-o<


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 Post subject: Re: How to separate Manmade Glass vs Obdisian vs Moldavite
PostPosted: Thu Dec 09, 2010 2:11 pm 
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First of all well come to Gemology online.

I want to answer your Question in two steps

1. How we can distinguished in Man Made Glass Vs Natural Glass [Obsidian(apache tear), Tektite (Modiviate)]

Mostly Man Made Glass RI is 1.50 or 1.51 or 1.52 or Greater the 1.52 and have Gas Bubble (Donut Shaped), Swirl lines. Mostly Man made Glass will Chalky appearance in UV.

Mostly Natural Glass have RI 1.49 and have a crystals, elongated gas bubbles in parallel arrangement (but some Donut shaped) and Flake like inclusion.

Step 2. How we can distinguished in Obsidian and Modiviate.

So it is very easy. The color of the obsidian is Brown to Black and The Color of the Modiviate is Green to Black. I have also seen a Modiviate of Yellow color such as Libia and I also seen a modiviate with andulsite crystal. I think the locality of this type modiviate is Peru (If I am not missing)

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Hamid Usman Khattak (HUK)_Pakistan

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 Post subject: Re: How to separate Manmade Glass vs Obdisian vs Moldavite
PostPosted: Sun Jan 26, 2014 12:02 pm 
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Can a Moldavite show 'snake-like band' under polariscope?


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 Post subject: Re: How to separate Manmade Glass vs Obdisian vs Moldavite
PostPosted: Sun Jan 26, 2014 2:49 pm 
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iwakasu wrote:
Can a Moldavite show 'snake-like band' under polariscope?

ADR (anomalous double refraction) is common in all glass, natural and man made.


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 Post subject: Re: How to separate Manmade Glass vs Obdisian vs Moldavite
PostPosted: Mon Jan 27, 2014 2:12 pm 
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Thanks Barbra.
Recently I got a parcel of green stones the sold as Green Obsidian. The RI is 1.51, somewhat ADR under polariscope and I see round and elongated gas bubbles as in these photos. The SG around
2.50-2.51 gr/cc

Are they natural or a kind of manmade glass sold as Obsidian? Thanks


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 Post subject: Re: How to separate Manmade Glass vs Obdisian vs Moldavite
PostPosted: Mon Jan 27, 2014 2:22 pm 
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Osman khattak wrote:
The color of obsidian is Brown to Black


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 Post subject: Re: How to separate Manmade Glass vs Obdisian vs Moldavite
PostPosted: Mon Jan 27, 2014 2:25 pm 
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Almost all of the "green obsidian" I have ever heard of ended up being man made glass. I have seen posts on this in the past on the USFG group.

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 Post subject: Re: How to separate Manmade Glass vs Obdisian vs Moldavite
PostPosted: Mon Jan 27, 2014 4:34 pm 
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I had thought that all green obsidian was melted bottles, but I have found solid references to it in the literature. There is also a rather obscure bright blue natural volcanic glass (not technically an obsidian, apparently it formed in the wall rock of a magma intrusion) which is found somewhere in the Alps.

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 Post subject: Re: How to separate Manmade Glass vs Obdisian vs Moldavite
PostPosted: Mon Jan 27, 2014 5:28 pm 
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Call me skeptical..... (I've been called worse) :wink:


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 Post subject: Re: How to separate Manmade Glass vs Obdisian vs Moldavite
PostPosted: Wed Jan 29, 2014 1:03 am 
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Back to Moldavite, I found a parcel of subtle-green stones with detailed etching all around, just like real Moldavite. I took closer look pictures to show how the details are. Is it real natural Moldavite or fake Molda can imitate the details?


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 Post subject: Re: How to separate Manmade Glass vs Obdisian vs Moldavite
PostPosted: Wed Jan 29, 2014 1:52 pm 
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Almost anything can be imitated. Impossible to tell from an image. Looks like Moldavite though.

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 Post subject: Re: How to separate Manmade Glass vs Obdisian vs Moldavite
PostPosted: Thu Jan 30, 2014 7:16 pm 
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Scarodactyl wrote:
There is also a rather obscure bright blue natural volcanic glass (not technically an obsidian, apparently it formed in the wall rock of a magma intrusion) which is found somewhere in the Alps.


A blue volcanic glass ? In the Alps ??? :roll:


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