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 5:56 am

All times are UTC - 4 hours




Post new topic Reply to topic  [ 12 posts ] 
Author Message
 Post subject: Tourmaline crystal cutting advice
PostPosted: Thu Jun 07, 2012 11:20 pm 
Offline
Valued Contributor

Joined: Thu Sep 24, 2009 3:44 pm
Posts: 151
Location: Kingman,Az
I have a crystal of what I believe is Rubellite Tourmaline.
The stone has closed "C" but is very transparent and medium saturation.
The crystal measurements are 25.5 cts. 40.1 mm long and is triangular @
7.3 mm x 6.9 mm x 7.1 mm

Would this stone be best cut as a single stone or a pair of stones.

Are there any recommendations on designs for this type of Tourmaline?
I am thinking it might be best cut in Jeff Graham's "Smith Bar" but was wondering if there are better performing designs?

Thanks

Harold

Image

Image

Image


Top
 Profile  
Reply with quote  
 Post subject: Re: Tourmaline crystal cutting advice
PostPosted: Fri Jun 08, 2012 2:57 am 
Offline
Site Admin
User avatar

Joined: Fri Apr 17, 2009 3:53 pm
Posts: 2049
Location: Sweden
I would probably go for a matched pair.

_________________
_____________
Conny Forsberg


Top
 Profile  
Reply with quote  
 Post subject: Re: Tourmaline crystal cutting advice
PostPosted: Fri Jun 08, 2012 7:54 am 
Offline
Gold Member
User avatar

Joined: Sat Sep 29, 2007 8:14 pm
Posts: 1383
Location: Royal Oak, Michigan US
Definitely, matching pair is the way to go.

As for it being labeled "Rubellite", well this could be a testy discussion as it does not quite fall into the "Rubellite" category. But, in some countries, anything pink to red is considered "Rubellite".

_________________
Warm regards,
Roger Dery
Royal Oak, Michigan US
http://www.rogerdery.com


Top
 Profile  
Reply with quote  
 Post subject: Re: Tourmaline crystal cutting advice
PostPosted: Fri Jun 08, 2012 8:07 am 
Offline
Valued Contributor

Joined: Fri Jan 06, 2012 7:06 pm
Posts: 238
Location: Michigan
I agree that cutting 2 stones would be better. If cut as one stone with a closed-C the ends are going to be very dark, and also those are some large / long facets to polish.
If cut into two stones, if you try and cut a matched pair,....they won't necessarily be the same exact color. Often when cutting a long crystal into multiple pieces the color will vary along the length. Darker, lighter / more or less saturated along the crystal.
--You probably already knew all this, but for those that don't.....


Top
 Profile  
Reply with quote  
 Post subject: Re: Tourmaline crystal cutting advice
PostPosted: Fri Jun 08, 2012 10:20 am 
Offline
Platinum Member
User avatar

Joined: Wed Mar 15, 2006 5:10 pm
Posts: 2117
Location: Maryland
I'd think about 3 stones. My experience is those long thin stones are a tough sell. With an opposed bar cut and the shape of the rough you should get a very high yield, so you could get maybe (2) 2.5 ct stones and (1) 3.5 ct. I'm thinking one rectangular and 2 more square bar cuts. Could make a nice set.

_________________
Precison Gem
www.precisiongem.com


Top
 Profile  
Reply with quote  
 Post subject: Re: Tourmaline crystal cutting advice
PostPosted: Fri Jun 08, 2012 10:27 am 
Offline
Site Admin
User avatar

Joined: Sun Oct 16, 2005 12:22 pm
Posts: 21602
Location: San Francisco
I agree with Gene.
Long narrow tourmalines are difficult to sell mounted, let alone loose.


Top
 Profile  
Reply with quote  
 Post subject: Re: Tourmaline crystal cutting advice
PostPosted: Fri Jun 08, 2012 2:14 pm 
Offline
Valued Contributor

Joined: Thu Jun 03, 2010 1:49 pm
Posts: 331
Location: South Africa
Hi Harold,

That is a beautiful crystal, a pity about the closed axis. An opposed bar would be a good choice. I think it was John Bailey who designed green 3 for closed c tourmaline, if I remember it is available on the USFG'S list, also If I remember correctly Lisa Elser did 2 variations of this, 1 with a step cut pavilion and one an enhanced version, both looked great. I tried the step cut pavilion option once and it worked very well.

Good luck,

Sean.


Top
 Profile  
Reply with quote  
 Post subject: Re: Tourmaline crystal cutting advice
PostPosted: Sat Jun 09, 2012 5:48 pm 
Offline
Valued Contributor

Joined: Thu Sep 24, 2009 3:44 pm
Posts: 151
Location: Kingman,Az
Thanks for all the recommendations for this piece of rough.

Does anyone know where to find Lisa Elser's designs for closed C axis stones.
I have googled and checked everywhere I know to check.

Thanks
Harold


Top
 Profile  
Reply with quote  
 Post subject: Re: Tourmaline crystal cutting advice
PostPosted: Sat Jun 09, 2012 7:03 pm 
Offline
Moderator
User avatar

Joined: Fri Jun 25, 2010 10:06 pm
Posts: 2267
Location: Chapel Hill, NC / Toronto, ON
Harold, Lisa's a frequent poster on here. You could probably just send her a PM and ask her for some designs. As far as I remember, she only has a few designs up here, and she doesn't have any on her website either.

Since member profiles are a bit hard to find sometimes, here's a direct link. (Mods, if I'm not allowed to direct-link people's profiles, feel free to delete this post.)


Top
 Profile  
Reply with quote  
 Post subject: Re: Tourmaline crystal cutting advice
PostPosted: Sat Jun 09, 2012 9:12 pm 
Offline
Platinum Member
User avatar

Joined: Wed Mar 15, 2006 5:10 pm
Posts: 2117
Location: Maryland
Use Jeff Grahm's Smith Bar. You can adjust it for any L/W ratio. Works well for closed C axis tourmaline.

_________________
Precison Gem
www.precisiongem.com


Top
 Profile  
Reply with quote  
 Post subject: Re: Tourmaline crystal cutting advice
PostPosted: Sun Jun 10, 2012 12:37 pm 
Offline
Valued Contributor
User avatar

Joined: Sat Jun 09, 2012 3:58 pm
Posts: 156
Location: Sweden
Personally I've been experimenting with a bufftop to show of the colour on a similar piece.

Pavilion:
I did two tiers on the pavilion @ 43* and one @ 46*, also one at 72* to hide off the black C axis.

On the crown I did finish one tier: 75*, only tier finished to polish on the faceting machine.
I also roughed in two sides at 36*, as a guide to get an even girdle.
After that I went to the cabbing machine to round it off and polish.

Image

I learned a few things, getting everything nice and even after transfer on a long cut can be hellish. Thinking about sawing several smaller ones does seem plausible..


Top
 Profile  
Reply with quote  
 Post subject: Re: Tourmaline crystal cutting advice
PostPosted: Tue Jun 12, 2012 11:55 am 
Offline
Valued Contributor

Joined: Thu Jun 03, 2010 1:49 pm
Posts: 331
Location: South Africa
Hi Harold,

You will find the Green 3 for closed c here, http://www.gemstoneartist.com/Designs.asp

The shape of the pavilion does tend to create an extinction as the stone is tilted. The crown is a scissors type cut and throws around some interesting reflections. A novel design to difficult material

The stepped pavilion option has 2 advantages in my opinion, not so much extinction and not so much depth of stone needed to complete the pavilion. Lisa used 46, 43 and 41 on the long sides only, keep the ends steep as in the original. Also your L/W will need to be accurate for the crown to make sense.

There were some pictures of the finished product on the transformation pages (16,17), no longer visible.


Top
 Profile  
Reply with quote  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 12 posts ] 

All times are UTC - 4 hours


Who is online

Users browsing this forum: No registered users and 29 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