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.
Post subject: Re: How to separate Manmade Glass vs Obdisian vs Moldavite
Posted: Thu Dec 09, 2010 2:11 pm
Gemology Online Veteran
Joined: Wed Dec 30, 2009 11:44 am Posts: 525 Location: PAKISTAN-Peshawar
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)
Post subject: Re: How to separate Manmade Glass vs Obdisian vs Moldavite
Posted: Mon Jan 27, 2014 2:12 pm
Established Member
Joined: Sun Jul 19, 2009 11:15 am Posts: 48 Location: indonesia
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
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.
Post subject: Re: How to separate Manmade Glass vs Obdisian vs Moldavite
Posted: Wed Jan 29, 2014 1:03 am
Established Member
Joined: Sun Jul 19, 2009 11:15 am Posts: 48 Location: indonesia
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?
Post subject: Re: How to separate Manmade Glass vs Obdisian vs Moldavite
Posted: Thu Jan 30, 2014 7:16 pm
Gold Member
Joined: Wed Jan 23, 2013 5:29 pm Posts: 1047 Location: Paris
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.
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