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?
Post subject: Re: Tourmaline crystal cutting advice
Posted: Fri Jun 08, 2012 7:54 am
Gold Member
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".
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.....
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.
Post subject: Re: Tourmaline crystal cutting advice
Posted: Fri Jun 08, 2012 2:14 pm
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.
Post subject: Re: Tourmaline crystal cutting advice
Posted: Sat Jun 09, 2012 7:03 pm
Moderator
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.)
Post subject: Re: Tourmaline crystal cutting advice
Posted: Sun Jun 10, 2012 12:37 pm
Valued Contributor
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.
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..
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.
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