October 3-7—JOSHUA TREE, CALIFORNIA: Annual show; Sportsmans Club of Joshua Tree
Welcome to the GemologyOnline.com Forum
A non-profit Forum for the exchange of gemological ideas
It is currently Thu Sep 20, 2018 10:56 pm

All times are UTC - 4 hours




Post new topic Reply to topic  [ 8 posts ] 
Author Message
 Post subject: Ruby in marble, probably from Afghanistan
PostPosted: Sat May 12, 2018 10:15 am 
Offline
New to the Forum or The Quiet Type

Joined: Mon Apr 16, 2018 7:25 am
Posts: 6
A specimen recently bought via eBay, ruby crystals in marble:

Image
Image
Image
Image
Image
Image

Backlit by the sun:
Image


Top
 Profile  
Reply with quote  
 Post subject: Re: Ruby in marble, probably from Afghanistan
PostPosted: Sun May 20, 2018 3:54 pm 
Offline
Gold Member

Joined: Sun Jun 28, 2009 9:56 am
Posts: 1213
octahedral crystals with [111] cleavage planes sounds more like spinel.


Top
 Profile  
Reply with quote  
 Post subject: Re: Ruby in marble, probably from Afghanistan
PostPosted: Sun May 20, 2018 4:59 pm 
Online
Moderator
User avatar

Joined: Mon Apr 02, 2012 9:31 pm
Posts: 2934
Location: North Carolina
Pseudooctahedral crystal form is very typical for rubies from that locale.


Top
 Profile  
Reply with quote  
 Post subject: Re: Ruby in marble, probably from Afghanistan
PostPosted: Sun May 20, 2018 7:09 pm 
Offline
Site Admin
User avatar

Joined: Sun Oct 16, 2005 12:22 pm
Posts: 18971
Location: San Francisco
What causes that habit, Stephen? Does it occur anywhere else?


Top
 Profile  
Reply with quote  
 Post subject: Re: Ruby in marble, probably from Afghanistan
PostPosted: Sun May 20, 2018 11:15 pm 
Online
Moderator
User avatar

Joined: Mon Apr 02, 2012 9:31 pm
Posts: 2934
Location: North Carolina
I am not sure what causes it. You see the same kind of formation in those winza rubies/sapphires among other locales.


Top
 Profile  
Reply with quote  
 Post subject: Re: Ruby in marble, probably from Afghanistan
PostPosted: Mon May 21, 2018 12:38 am 
Offline
Gold Member

Joined: Sun Jun 28, 2009 9:56 am
Posts: 1213
Interesting, very misleading habit. That's why I always reserve judgment when interpretating a crystal habit just from sight, which can often be deceptive unless precisely measuring the angles (I might want to get a goniometer some day..)


Top
 Profile  
Reply with quote  
 Post subject: Re: Ruby in marble, probably from Afghanistan
PostPosted: Mon May 21, 2018 7:30 am 
Online
Moderator
User avatar

Joined: Mon Apr 02, 2012 9:31 pm
Posts: 2934
Location: North Carolina
Yeah, it's really unnerving the first time you see it. 'Corundum, I thought we were friends. How could you betray me like this?'


Top
 Profile  
Reply with quote  
 Post subject: Re: Ruby in marble, probably from Afghanistan
PostPosted: Mon May 21, 2018 4:21 pm 
Offline
New to the Forum or The Quiet Type

Joined: Mon Apr 16, 2018 7:25 am
Posts: 6
Thanks guys. It's funny you should say spinel as that it what it was sold as on eBay. However, the giveaway it's corundum is the fine polysynthetic twinning lines on the rhombohedral faces, and the triangular-looking terminations have the striations at 60 degree angles to each other. The rhombohedral faces are dominant which give it the sort of pseudo-octahedral look. The prismatic faces can be seen in picture 5, which have the grooved appearance.

I got it at a very good price too.


Top
 Profile  
Reply with quote  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 8 posts ] 

All times are UTC - 4 hours


Who is online

Users browsing this forum: Google [Bot] and 1 guest


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