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 5:41 pm

All times are UTC - 4 hours




Post new topic Reply to topic  [ 7 posts ] 
Author Message
 Post subject: Tourmaline
PostPosted: Fri Dec 18, 2009 12:38 pm 
Offline
Active Member
User avatar

Joined: Thu Dec 18, 2008 11:34 am
Posts: 95
Location: UK
hi there all...i hope you are all well.... the exams are looming!!

And i'm just browing tourmaline....can someone just confirm to me, although i did read it in a chat, but i can't find it now.....very annoying... If we want to make the the colour look darker, we cut Tourmaline with c axis at 90 degrees to the table?? And if we want it lighter, then parallel with the table? is this correct or is it the other way round!!!

Thanks
Pix xxx


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Fri Dec 18, 2009 1:46 pm 
Offline
Site Admin
User avatar

Joined: Fri Apr 17, 2009 3:53 pm
Posts: 2049
Location: Sweden
That is generally right yes.
The stone usually looks darker when you have the C-axis orientated so that you look down the C when viewing through the table.

_________________
_____________
Conny Forsberg


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Fri Dec 18, 2009 2:08 pm 
Offline
Moderator
User avatar

Joined: Thu Dec 13, 2007 3:42 pm
Posts: 4091
Location: the Netherlands
Only slightly related but still fun:

Did you know the very first polariscopes were composed out of two slices of tourmaline? (which was possible because one of the rays (forgot which one) can get fully absorbed thus making the slice a polarizing sheet)


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Fri Dec 18, 2009 7:35 pm 
Offline
Gemology Online Übergoddess

Joined: Tue Nov 06, 2007 3:16 am
Posts: 3170
8) even though i've never used a polariscope, that's very interesting, tim!! thanks for sharing that with us!! interesting site, too!! and if you have questions, you have to fill out a web form for further info. ?


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Sun Dec 20, 2009 4:46 pm 
Offline
Active Member
User avatar

Joined: Thu Dec 18, 2008 11:34 am
Posts: 95
Location: UK
Thanks Connie, Tim :smt023

Happy Christmas to u all.....

Pix x x x


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Tue Apr 06, 2010 1:49 pm 
Offline
Established Member
User avatar

Joined: Fri Apr 02, 2010 11:47 am
Posts: 19
Location: Islamabad/Pakistan
Hi,
This is not always the case watermalons and some others having dark outer coating of other colors may be look lighter from C-axis and dark from a-b axis.
Don't mind if you feel i am wrong.

_________________
I only trust the one which is faceted by myself,whether it is badly cut or well cut.


Top
 Profile  
Reply with quote  
 Post subject: Re: Tourmaline
PostPosted: Sat Nov 06, 2010 12:43 am 
Tourmaline is strongly doubly refractive and pleochroic (even stronger than zircon or peridot) One being much darker than the other. Cutters try to orientate the gems table so the lighter pleochroic colour is visible.
However to darken pale rough you orientate the table so its perpendicular to the crystals length and vise verse. You also have to think about cleavage and stability though when deciding on cutting direction.
Hope that helps.


Top
  
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 7 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