January 24 Through February 4—TUCSON, ARIZONA: Annual show
Welcome to the GemologyOnline.com Forum
A non-profit Forum for the exchange of gemological ideas
It is currently Thu Mar 28, 2024 8:19 am

All times are UTC - 4 hours




Post new topic Reply to topic  [ 19 posts ]  Go to page 1, 2  Next
Author Message
 Post subject: How to separate Manmade Glass vs Obdisian vs Moldavite
PostPosted: Mon Dec 06, 2010 1:56 am 
Offline
Established Member

Joined: Sun Jul 19, 2009 11:15 am
Posts: 48
Location: indonesia
Since that three igneous rock species could overlap in visual and physical characteristics, then how can we separate them? Thanks.......


Top
 Profile  
Reply with quote  
 Post subject: Re: How to separate Manmade Glass vs Obdisian vs Moldavite
PostPosted: Mon Dec 06, 2010 5:20 am 
Offline
Site Admin
User avatar

Joined: Fri Apr 17, 2009 3:53 pm
Posts: 2049
Location: Sweden
I would use the microscope and study internal characteristics.

_________________
_____________
Conny Forsberg


Top
 Profile  
Reply with quote  
 Post subject: Re: How to separate Manmade Glass vs Obdisian vs Moldavite
PostPosted: Tue Dec 07, 2010 1:02 pm 
Offline
Valued Contributor

Joined: Fri Sep 08, 2006 8:20 pm
Posts: 354
Location: Texas
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.


Top
 Profile  
Reply with quote  
 Post subject: Re: How to separate Manmade Glass vs Obdisian vs Moldavite
PostPosted: Tue Dec 07, 2010 1:14 pm 
Offline
Established Member

Joined: Thu Jul 16, 2009 9:27 am
Posts: 41
Location: Sri Lanka
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<


Top
 Profile  
Reply with quote  
 Post subject: Re: How to separate Manmade Glass vs Obdisian vs Moldavite
PostPosted: Thu Dec 09, 2010 2:11 pm 
Offline
Gemology Online Veteran
User avatar

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)

With best Regards

Hamid Usman Khattak (HUK)_Pakistan

_________________
Gemology for everyone.
HUK


Top
 Profile  
Reply with quote  
 Post subject: Re: How to separate Manmade Glass vs Obdisian vs Moldavite
PostPosted: Sun Jan 26, 2014 12:02 pm 
Offline
Established Member

Joined: Sun Jul 19, 2009 11:15 am
Posts: 48
Location: indonesia
Can a Moldavite show 'snake-like band' under polariscope?


Top
 Profile  
Reply with quote  
 Post subject: Re: How to separate Manmade Glass vs Obdisian vs Moldavite
PostPosted: Sun Jan 26, 2014 2:49 pm 
Offline
Site Admin
User avatar

Joined: Sun Oct 16, 2005 12:22 pm
Posts: 21602
Location: San Francisco
iwakasu wrote:
Can a Moldavite show 'snake-like band' under polariscope?

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


Top
 Profile  
Reply with quote  
 Post subject: Re: How to separate Manmade Glass vs Obdisian vs Moldavite
PostPosted: Mon Jan 27, 2014 2:12 pm 
Offline
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


Attachments:
IMG_0688.JPG
IMG_0688.JPG [ 49.53 KiB | Viewed 6933 times ]
IMG_0688.JPG
IMG_0688.JPG [ 49.53 KiB | Viewed 6933 times ]
IMG_0687.JPG
IMG_0687.JPG [ 27.96 KiB | Viewed 6933 times ]
Top
 Profile  
Reply with quote  
 Post subject: Re: How to separate Manmade Glass vs Obdisian vs Moldavite
PostPosted: Mon Jan 27, 2014 2:22 pm 
Offline
Site Admin
User avatar

Joined: Sun Oct 16, 2005 12:22 pm
Posts: 21602
Location: San Francisco
Osman khattak wrote:
The color of obsidian is Brown to Black


Top
 Profile  
Reply with quote  
 Post subject: Re: How to separate Manmade Glass vs Obdisian vs Moldavite
PostPosted: Mon Jan 27, 2014 2:25 pm 
Offline
Valued Contributor
User avatar

Joined: Mon Dec 24, 2012 5:16 pm
Posts: 234
Location: Austin, Texas
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.

_________________
"Distracted by something shiny."

Wayne Wilson


Top
 Profile  
Reply with quote  
 Post subject: Re: How to separate Manmade Glass vs Obdisian vs Moldavite
PostPosted: Mon Jan 27, 2014 4:34 pm 
Offline
Moderator
User avatar

Joined: Mon Apr 02, 2012 9:31 pm
Posts: 4015
Location: North Carolina
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.

_________________
Rough and cut classic and exotic synthetic gems:https://store.turtleshoard.com


Top
 Profile  
Reply with quote  
 Post subject: Re: How to separate Manmade Glass vs Obdisian vs Moldavite
PostPosted: Mon Jan 27, 2014 5:28 pm 
Offline
Site Admin
User avatar

Joined: Sun Oct 16, 2005 12:22 pm
Posts: 21602
Location: San Francisco
Call me skeptical..... (I've been called worse) :wink:


Top
 Profile  
Reply with quote  
 Post subject: Re: How to separate Manmade Glass vs Obdisian vs Moldavite
PostPosted: Wed Jan 29, 2014 1:03 am 
Offline
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?


Attachments:
IMG_0698.JPG
IMG_0698.JPG [ 57.93 KiB | Viewed 6898 times ]
IMG_0696.JPG
IMG_0696.JPG [ 63.85 KiB | Viewed 6898 times ]
IMG_0695.JPG
IMG_0695.JPG [ 47.97 KiB | Viewed 6898 times ]
Top
 Profile  
Reply with quote  
 Post subject: Re: How to separate Manmade Glass vs Obdisian vs Moldavite
PostPosted: Wed Jan 29, 2014 1:52 pm 
Offline
Site Admin
User avatar

Joined: Fri Apr 17, 2009 3:53 pm
Posts: 2049
Location: Sweden
Almost anything can be imitated. Impossible to tell from an image. Looks like Moldavite though.

_________________
_____________
Conny Forsberg


Top
 Profile  
Reply with quote  
 Post subject: Re: How to separate Manmade Glass vs Obdisian vs Moldavite
PostPosted: Thu Jan 30, 2014 7:16 pm 
Offline
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.


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


Top
 Profile  
Reply with quote  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 19 posts ]  Go to page 1, 2  Next

All times are UTC - 4 hours


Who is online

Users browsing this forum: No registered users and 8 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group
Gemology Style ported to phpBB3 by Christian Bullock