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 2:58 pm

All times are UTC - 4 hours




Post new topic Reply to topic  [ 7 posts ] 
Author Message
 Post subject: Is heating possible with red to violet spinel
PostPosted: Sun Nov 03, 2013 4:06 am 
Offline
New to the Forum or The Quiet Type

Joined: Thu Oct 31, 2013 3:15 am
Posts: 8
Hi,

Does anybody have any information to share regarding spinel heat treatment.
I have few red to violet dark spinels. is there any recipe to lighten its colour. i will post a image in the next post.
I tried my best to find something. but I could not find anything special.
I could hear few incidents like violet spinel getting lightened after treating. which was wrongly identified as a sapphire. I hope he should have treated it to remove blue to make it pink.
but i doubt that will this work with spinel. if the answer is yes to which extent is it successful.
if anybody can clarify i will be grateful.

regards
Risly


Top
 Profile  
Reply with quote  
 Post subject: Re: Is heating possible with red to violet spinel
PostPosted: Sun Nov 03, 2013 8:25 pm 
Offline
Moderator
User avatar

Joined: Mon Apr 02, 2012 9:31 pm
Posts: 4015
Location: North Carolina
viewtopic.php?f=24&t=3445&p=161001
Unless something has changed in the mean time, generally spinel is not known to improve with heating or really any other treatment.

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


Top
 Profile  
Reply with quote  
 Post subject: Re: Is heating possible with red to violet spinel
PostPosted: Wed Nov 20, 2013 3:56 pm 
Offline
Moderator
User avatar

Joined: Thu Dec 13, 2007 3:42 pm
Posts: 4091
Location: the Netherlands
Scarodactyl wrote:
http://www.gemologyonline.com/Forum/phpBB2/viewtopic.php?f=24&t=3445&p=161001
Unless something has changed in the mean time, generally spinel is not known to improve with heating or really any other treatment.

Yes it does, both clarity and color can be positively affected by relatively low heat. It even says so in a link posted in the thread you link to :P

Read also: http://static.squarespace.com/static/50 ... tments.pdf


Top
 Profile  
Reply with quote  
 Post subject: Re: Is heating possible with red to violet spinel
PostPosted: Wed Nov 20, 2013 5:11 pm 
Offline
Moderator
User avatar

Joined: Mon Apr 02, 2012 9:31 pm
Posts: 4015
Location: North Carolina
That's really interesting. The link to that PDF in the thread itself didn't work so I was going by what others had said there (and what I've read elsewhere, though it must have been outdated info).

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


Top
 Profile  
Reply with quote  
 Post subject: Re: Is heating possible with red to violet spinel
PostPosted: Wed Nov 20, 2013 5:37 pm 
Offline
Moderator
User avatar

Joined: Thu Dec 13, 2007 3:42 pm
Posts: 4091
Location: the Netherlands
What is remarkable is that Chris doesn't encounter much heated stuff in his lab. All this is done in oxidizing atmospheres at temperatures one can easily achieve.

Could it be cause sleepy spinels are good sellers?


Top
 Profile  
Reply with quote  
 Post subject: Re: Is heating possible with red to violet spinel
PostPosted: Sun Nov 24, 2013 9:16 am 
Offline
Site Admin
User avatar

Joined: Fri Apr 17, 2009 3:53 pm
Posts: 2049
Location: Sweden
It is easily detected by Raman so should not cause much problem. There are also some spinels that are affected negatively colourwise, or so I have been told anyway. That might be a reason to be restrictive with heating which then will be less common. Just a theory.

_________________
_____________
Conny Forsberg


Top
 Profile  
Reply with quote  
 Post subject: Re: Is heating possible with red to violet spinel
PostPosted: Tue Sep 16, 2014 8:19 pm 
Offline
Gold Member

Joined: Mon May 26, 2014 9:42 pm
Posts: 1033
Weird - I read the paper you pointed to and it seemed to say that "this treatment was not being performed to improve color, since their experiments showed either little to no color modification or a less desirable color resulted from the heating. However, they did find that the transparency of certain spinels could be significantly improved by heating at temperatures between approximately 950C and 1150C"

Did you point to the wrong paper?


Top
 Profile  
Reply with quote  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 7 posts ] 

All times are UTC - 4 hours


Who is online

Users browsing this forum: No registered users and 15 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