Closed C

[nader]

Hello,

Awhile ago I had bought a 5.8 ct IF verdelite tourmaline from a new deposit in Congo and at the time I did not know the c-axis was closed. I guess I should have assumed this but i guess I wasn't really thinking about it at the time. I was wondering though, how much does a closed c on tourmaline affect the value of it? It's a rather richly saturated green so the closed c doesn't really help with that since it only appears to deepen the colour. The seller told me all of the green tourmaline from Congo is closed c and that it's still worth a good amount, but I don't see why people would want to have such a dark-looking stone...

 

[Jacki]

ANy pictures?

 

[PrecisionGem]

Is this a cut stone, or rough?

Much of the Congo tourmaline is close, but not all. I have seen some very nice pieces that are open with a blue/green color.

With the closed axis tourmalines, I usually cut an opposed bar design. If the end facets are cut to a large angle like 70 degress, then it will help to limit the effect of the dark axis. Actually, the opposed bar designs work better with a closed axis or partially closed stone then an open one. With the proper cutting, these closed axis tourmalines can be very attractive, cut wrong and they just get way too dark.

 

[nader]

Sorry for the bad lighting/quality although its not much lighter than the pic shows. it is a nicer green in person though...

It's an octagon wtih long-step facet crown and Barion pavilion. the cut itself is decent but an opposed bar would be so much nicer! I would LOVE to get it recut, although how much ct weight do you think would be lost (not that im really worried)

 

[PrecisionGem]

Here is a pretty typical oppossed bar cut. The length to width ratio can be changed to fit the stone. If your emerald cut has a keel pavilion, then your weight loss shouldnt be too much. However if they cut the ends in at maybe 45 degree angles, then more stone would need to be cut away. I would think your yield would be 50-65% on recutting.