Best stones for an opposed bar cut?

[beaujolais]

What would be good stones for an opposed bar cut? I''m thinking something with a good RI to show off the rolling flash of color. Spinel (but I don''t see any in opposed bar ever)? Garnet? There are a few in tourmaline but I''m wondering if that is really a good stone for this cut.

Thanks.

 

[Harriet]

Tourmaline, being dichroic, is great for the cut. I love the blue-green ones.

 

[Kelli]

I think I''ve really only seen tourmalines in that cut, but I haven''t been looking for very long. I''ve seen some really pretty ones though. I always notice the pinks

 

[Richard M.]

Kelli,

Opposed-bars can be cut in any material if it''s shaped right. It''s most popular in tourmalines and other minerals that crystallize in long, narrow shapes to take advantage of the weight savings. It''s also a very attractive cut IMO and there are several variations.

You probably won''t see it in natural sapphires, rubies, spinels or emeralds but it can easily be done in materials like quartz, aqua, morganite, yellow beryl, some garnets and topaz and some other gems.

Richard M.

 

[beaujolais]

Oh, that's what it is. Thanks Harriet & Richard. Now I get it. (Such great minds here !)

Harriet, you mean it would show both blue & green more in that cut? At the same time?

Kelli, what site do you see the pinks on? Thanks for the reply, too.

I seem to like that cut even though I've never had one. Tell me, though, that is a more "tasteful" cut than a checkerboard or am I thinking the wrong thing?

 

[Kelli]

Date: 10/24/2008 1:40:04 AM
Author: Richard M.
Kelli,

Opposed-bars can be cut in any material if it''s shaped right. It''s most popular in tourmalines and other minerals that crystallize in long, narrow shapes to take advantage of the weight savings. It''s also a very attractive cut IMO and there are several variations.

You probably won''t see it in natural sapphires, rubies, spinels or emeralds but it can easily be done in materials like quartz, aqua, morganite, yellow beryl, some garnets and topaz and some other gems.

Richard M.

Thanks Richard! I''d love to see an aqua in that cut! Would an ametrine work for that? I think I''ve seebn bi-color tourmalines but I don''t know enough about gemstones to know what would look nice.

 

[Kelli]

Date: 10/24/2008 1:46:09 AM
Author: sonomacounty
Oh, that''s what it is. Thanks Harriet & Richard. Now I get it. (Such great minds here !)

Harriet, you mean it would show both blue & green more in that cut? At the same time?

Kelli, what site do you see the pinks on? Thanks for the reply, too.

I seem to like that cut even though I''ve never had one. Tell me, though, that is a more ''tasteful'' cut than a checkerboard or am I thinking the wrong thing?

I don''t remember off the top of my head, but as soon as I find one (or more), I''ll let you know. That could be tomorrow morning, as it''s getting pretty late here!

 

[Kelli]

There are two on this page. I''ll see if I can find more in the morning.
http://finewatergems.com/Gallery.html

 

[Kelli]

I was also thinking of this one, but when I went back I reailzed it wasn''t pink. Here it is anyway

http://www.gemrite.com/cubecart/index.php?act=viewProd&productId=81

 

[Kelli]

But here is a zig-ziggy pink one
http://www.gemrite.com/cubecart/index.php?act=viewProd&productId=83

 

[Kelli]

And here are two from Richard''s site. One isn''t really pink, but I liked it so much I wanted to post it. I hope that''s ok

http://www.artcutgems.com/item.php?item_id=325&page=2&category_id=49

and
http://www.artcutgems.com/item.php?item_id=545&page=1&category_id=49

ok, really going to bed now!

 

[Richard M.]

Really clean aquas would look great if the rough was shaped right, especially if cut from a smaller crystal. Ametrine can be cut that way -- I just sold a barrel-cut ametrine, which is a variation on the opposed-bar. Again, finding the right rough is key. Its a great cut in citrine, lemon quartz, amethyst, etc.

Richard M.

 

[Kelli]

Date: 10/24/2008 2:17:43 AM
Author: Richard M.
Really clean aquas would look great if the rough was shaped right, especially if cut from a smaller crystal. Ametrine can be cut that way -- I just sold a barrel-cut ametrine, which is a variation on the opposed-bar. Again, finding the right rough is key. Its a great cut in citrine, lemon quartz, amethyst, etc.

Richard M.

Thanks for the great information! I''m just getting into colored gems and it''s a lot of fun!

 

[PrecisionGem]

I think the opposed bar designs work best in darker materials. They are often cut in tourmaline that have a closed C axis, as the this axis is almost eliminated by the cutting style. I have seen some in other materials, including lighter stones, but the effect gets lost. With a darker stone, as you rock the stone, it looks like neon lights flashing up and down, with a strong contrast against the facets that are not flashing.

 

[Harriet]

Sonoma,
Yes, you can see both colours. Gene has cut a number of gorgeous specimens. For a pin and blue(?) one, look at Jeff White''s website.

 

[beaujolais]

Thanks all. I''ve learned so much with this thread. I really do appreciate it.

Gene - you do some awesome things.

Can someone explain this to me, though: "They are often cut in tourmaline that have a closed C axis, as the this axis is almost eliminated by the cutting style."

I''m a little familiar with the axis thing but eliminating it means what?

Thanks so very much.

Sonoma

 

[Richard M.]

Gene, I agree the cut may work best in darker materials but I''m going to try it in clear quartz or Danburite soon just to see the effect.

I''ll let Harriet and you field the closed/cross-colored c-axis question since you two brought it up

Richard M.

 

[chrono]

A closed C axis is where the longer ends of the stone is dark - by eliminating this using the opposed bar design, the ends will now show colour instead of a darkish, almost black colour.

 

[Harriet]

Date: 10/24/2008 8:32:40 PM
Author: Richard M.
I''ll let Harriet and you field the closed/cross-colored c-axis question since you two brought it up

I was going to let Gene field the question since he taught me about c and a-b axes, but I see someone beat us to it.

 

[PrecisionGem]

A lot of tourmaline crystals look like a pencil. The long axis is the C axis. Often this axis is completely closed. This means if you look down it, you see no light, totally black. SOmetimes you get a real pretty blue green on the stone, but the C axis is an ugly olive color. So certain cuts and almost eliminate the effect of this axis on the stone. What you want to do is cut it with very a very steep angle on the ends. If you didn''t the stone would become very very dark, or the undesirable color of the C axis would fill the stone.

When buying rough, the price of open axis well colored tourmaline is often 2 or 3 times the price of a closed axis stones, since it leaves so many more options for cutting.

 

[Richard M.]

I would only add that the opposed-bar cut isn''t the only option when cutting closed-C crystals. Regular table cuts (emerald cuts and variations) work well if the ends are cut with a steep angle. I''ve even cut some closed-C stones in table cuts with steep sides (direction of c-axis) and regular angles on the end that performed well.

Richard M.

 

[Sagebrush]

Gene,

I agree with you about green tourmaline. When I started buying in Brazil in the mid 80s we could buy really thick trigonal crystals with lovely green to blue green A-B axis and perfect terminations. Now don''t drool, but I remember a small parcel with stones weighing 15-20 carats each, flawless with green leading to strong greenish blue at the termination. We cut a fabulous 9 carat opposed bar that actually ran from green to blue.

Some of the newer pieces on your site are great.

 

[stryeyes102]

I found this stone a few days ago and thought id toss it in here for those who asked; Mainly Richard M.

Its from Sacred Geometrics- A stunning 4.45 Carat white topaz (If this shouldn''t be posted please report- i wasn''t sure but, i didn''t want to post it without recognition to the site)


Enjoy

 

[stryeyes102]

Heres a second shot of it:

 

[PrecisionGem]

To me, that topaz looses the effect of an opposed bar cut, that you see in darker material. The effect is best when facets are either ON or OFF, just like LEDs lighting up.

 

[Richard M.]

Gene,

You''re looking at it in a 2-D image. In 3-D, with movement, the scintillation from white or lightly saturated materials can be as eye-catching as the off-on effect you mention. I appreciate both and think it''s a matter of personal preference.

Richard M.

 

[beaujolais]

The opposed bar cut fascinates me. It''s on my list for "someday".

 

[Harriet]

Sonoma,
Check out this one: http://www.precisiongem.com/html/html/GreenTourmaline.html
And this: http://www.whitesgems.com/gems/TML026.htm

 

[beaujolais]

Ah, Harriet, yes. There are a few I like at Precision Gem. Jeff's is gorgeous but very expensive.

I must behave for awhile thought, as I just got this 1.37 old miners (see avitar) and now have to set it:

https://www.pricescope.com/community/threads/my-new-vintage-stone-omc.98874/

Thanks so much for the links. From photo, it seems like the opposed bars would be fun. Do tell me, though, they are on a whole other level than a checkerboard cut?

Do you have any opposed bars?

Thanks, Sonoma

 

[Harriet]

I don''t have any opposed bar cut gems, but I do think they are a fabulous way to show off a dichroic stone. Checkerboards don''t do anything for me. One dealer warned me that checkerboards are sometimes used to hide inclusions.