gemfeller
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Post by gemfeller on Jul 6, 2024 14:24:14 GMT -5
I love Koroit Opal for the intricate designs it produces. It's not always flashy, colorful opal though when it is its spectacular. Much of it, to my eye, resembles a style of Aboriginal art, the black-and-white almost skeleatal-looking paintings of animals and other scenes. This is a cab I cut the other day from a little slab of rough that's been sitting on my bench for a long time. It has a few bright sparks of red and green that don't show up wall in the image, but I really like it for the eye-catching patterns and color variations it displays. Maybe you will too. ![](https://rockshow.rocktumblinghobby.com/i.php?/upload/2024/06/17/20240617122456-ac4e72bc-me.jpg)
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Post by opalpyrexia on Jul 6, 2024 15:30:14 GMT -5
That's a beauty, Rick! That's far more appealing that the few Koroit pieces that I've seen.
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rockbrain
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Post by rockbrain on Jul 6, 2024 15:45:14 GMT -5
That's sweet!
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dreamrocks
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Post by dreamrocks on Jul 6, 2024 15:52:14 GMT -5
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Post by rockjunquie on Jul 6, 2024 16:11:35 GMT -5
Beautiful cab, Rick. I agree with you on the patterns. If the pattern is great, the opal is just icing on the cake. ![:)](//storage.proboards.com/forum/images/smiley/smiley.png)
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khara
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Post by khara on Jul 6, 2024 16:46:39 GMT -5
I love Boulder Opal! I have a few small pieces I picked up years ago and am waiting to get better before cutting. With regular opal my understanding is the idea is to remove the matrix and find the flash and then not grind it out too far. With this type of opal, is it more like just cutting a standard cab? I mean, it seems there would still be some degree of finding the color and not grinding so far that you lose it, but also just balancing that with basically cutting a standard cab shape? If that makes sense?
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gemfeller
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Post by gemfeller on Jul 6, 2024 20:00:45 GMT -5
I love Boulder Opal! I have a few small pieces I picked up years ago and am waiting to get better before cutting. With regular opal my understanding is the idea is to remove the matrix and find the flash and then not grind it out too far. With this type of opal, is it more like just cutting a standard cab? I mean, it seems there would still be some degree of finding the color and not grinding so far that you lose it, but also just balancing that with basically cutting a standard cab shape? If that makes sense? Well, sort of.... There are several different types of boulder opal and it can be one of the brightest and most valuable opals from Oz. But there's also a strong appreciation that seems to be growing in recent years for the not-so-colorful stones that have intricate and unusual patterns from the Koroit locality, as shown in my stone. I lost a bit of color in cutting it, in fact, because the pattern seemed more pleasing to me. There's one vividly-colored type that yields incredibly beautiful gems called Churchwindows. They actually resemble stained-glass windows in churches and cathedrals with the light shining through them. Another type features thin layers of amazingly bright and valuable opal on very dark brown or blackish ironstone. Many Koroit types have spiderweb networks of very bright multicolored opal interwoven through the dark ironstone. Yowah "nuts" are ironstone concretions that have "kernels' of blindingly-bright and beautiful opal in thrilling patterns. I could write a book. In fact, many others have. One that gives a general over-view of most types of opal and localities, with great pictures, is "Opal: The Phenomenal Gemstone" published by Lithographie LLC, East Hampton CT. It's a luxury paperback and expensive for a paperback but worth it if you're an opal fanatic like me. ETA: I kind of overlooked your question about cutting. My experience with cutting boulder types is "anything that works!" Each type presents different challenges --whether with shaping or trimming or polishing -- and flexibility is needed to meet them. And a warning: when cutting ironstone opals, plan on ending up with your clothes and skin stained bright red. They're ultra-messy.
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Post by hummingbirdstones on Jul 7, 2024 0:58:24 GMT -5
gemfeller Rick, that's a banger! Lucky you having the dark brown ironstone that actually takes a polish.
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khara
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Post by khara on Jul 7, 2024 4:15:40 GMT -5
Interesting info gemfeller I do know the ones I have are Koroit. They weren’t cheap. One may have to be a learning project. Hopefully I don’t screw them up. They do have great colors and patterns showing. I’m actually not much of an opal person in general, but these koroit and boulder ones, I just love the colors running through the matrix.
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Post by liveoak on Jul 7, 2024 6:29:20 GMT -5
WOW ! What a cab that is !! The colors & pattern are really wonderful. Almost looks like mother-of-pearl in the swirls.
Nice one !
Patty
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gemfeller
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Post by gemfeller on Jul 7, 2024 11:53:58 GMT -5
Interesting info gemfeller I do know the ones I have are Koroit. They weren’t cheap. One may have to be a learning project. Hopefully I don’t screw them up. They do have great colors and patterns showing. I’m actually not much of an opal person in general, but these koroit and boulder ones, I just love the colors running through the matrix. They're really not hard to cut but... The trick with Koroit and ironstsone boulder in general, is being able to judge the hardness of the matrix. Some is so soft it comes off on the wheels like butter. That's usually the light-colored tans. In general, the darker, the better the polish. Some takes a brilliant polish. However when light and dark are blended in the same stone, undercutting can be a serious issue.
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Post by hummingbirdstones on Jul 7, 2024 12:08:21 GMT -5
Interesting info gemfeller I do know the ones I have are Koroit. They weren’t cheap. One may have to be a learning project. Hopefully I don’t screw them up. They do have great colors and patterns showing. I’m actually not much of an opal person in general, but these koroit and boulder ones, I just love the colors running through the matrix. khara how big are your pieces? Can you post some pictures? We might be able to give you a little guidance on where to start.
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khara
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Post by khara on Jul 7, 2024 16:13:58 GMT -5
gemfeller hummingbirdstones Thanks for the info about the light and dark matrix. That’s good to know. I will dig them out and take a look at the coloring and post some pics.
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Post by jasoninsd on Jul 15, 2024 23:10:03 GMT -5
Rick, that is just amazingly beautiful. Fantastic job on that one! You're really making me want to tackle this piece of Karoit I got from hummingbirdstones . I'm torn on how to work this one because I don't want to lose a millimeter of the surface... ![](https://res.cloudinary.com/dm7ae3itr/image/upload/v1721102939/byy00b8zchyhhzw4kqcu.jpg) ![](https://res.cloudinary.com/dm7ae3itr/image/upload/v1721102940/cv6xdu1qfqgpodehvedb.jpg) ![](https://res.cloudinary.com/dm7ae3itr/image/upload/v1721102940/e0ibwoxduvorx1tv0swq.jpg)
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gemfeller
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Post by gemfeller on Jul 16, 2024 0:48:51 GMT -5
jasoninsd The Koroit cab you posted in your recent thread is a knock-out. It beats mine all to heck, especially in coloration. It seems to me you know how to cut this material. The current piece does present some challenges. It's hard to tell for sure from your images but it may be that you're stuck with a curved-bottom stone if I'm reading the pictures right. I'm assuming the part with the lovely patterns is the flattest surface. The tragedy with this material is that to cut it you often have to sacrifice some beauty. Deciding what to cut away and what to keep can cause a lot of distress. I have a piece of rough that's gem quality. But....deciding how to slab it gives me nightmares. I'll try to get pictures of it soon and post them to show my dilemma. If I get it right the result will be crackers as my Aussie friends say.
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Post by jasoninsd on Jul 16, 2024 7:59:01 GMT -5
jasoninsd The Koroit cab you posted in your recent thread is a knock-out. It beats mine all to heck, especially in coloration. It seems to me you know how to cut this material. The current piece does present some challenges. It's hard to tell for sure from your images but it may be that you're stuck with a curved-bottom stone if I'm reading the pictures right. I'm assuming the part with the lovely patterns is the flattest surface. The tragedy with this material is that to cut it you often have to sacrifice some beauty. Deciding what to cut away and what to keep can cause a lot of distress. I have a piece of rough that's gem quality. But....deciding how to slab it gives me nightmares. I'll try to get pictures of it soon and post them to show my dilemma. If I get it right the result will be crackers as my Aussie friends say. I truly was not trying to be coy in my post...I really am stumped on this one. I've been pondering it for weeks...not constantly...but off and on! LOL I think I "get" how to polish the face of Karoit cabs...but how and what to sacrifice on this one while shaping it has me stumped. I couldn't see a way around not having a curved bottom stone...and still maintain a decent sized face on it. Sounds like that may actually be what's necessary... I'm actually fascinated with opal cutting...which scares me - or at least it scares my wallet! LOL - With other material, I have a slab...look for a cool pattern...try to work the dome so I don't lose the pattern...or try and compensate for how the pattern is going to change when doming. Opal cutting is like that too...just on steroids! LOL Rick, that is just amazingly beautiful. Fantastic job on that one! You're really making me want to tackle this piece of Karoit I got from hummingbirdstones . I'm torn on how to work this one because I don't want to lose a millimeter of the surface... I know this is heresy, but with a piece that undefined, can't you just work the all the angles and call it day?
One of my favorite pieces of all time is from Rookie Rockhound out of Australia.
He just let the rock dictate the work. Again I'm out of my league, but this seems like one of those where you use what you have opportunities are given to you...
I think that just might be the case here Chad! I don't think this piece has a way of becoming traditional in any sense...
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gemfeller
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Post by gemfeller on Jul 16, 2024 12:52:52 GMT -5
jasoninsd I wasn't suggesting you were being coy. I was trying to buck up your confidence. I started out cutting opal many years ago. I was poor. I remember waiting anxiously 3 months for 1 ounce of rough from Oz because it was shipped by sea mail and I couldn't afford air postage. I've been through many twists and turns with the lovely stuff since. I've experienced the same feelings you're going through many times. And still! Here are some images of the frustrating piece of Koroit rough I mentioned earlier in the thread. I think I've finally come up with a slabbing strategy but I'm almost afraid to try it for fear of messing up an irreplaceable natural creation. But that's opal cutting! Side View ![](https://rockshow.rocktumblinghobby.com/i.php?/upload/2024/07/16/20240716104429-1574b23d-me.jpg) Long Top View ![](https://rockshow.rocktumblinghobby.com/i.php?/upload/2024/07/16/20240716104558-f6656282-me.jpg) Close Top View ![](https://rockshow.rocktumblinghobby.com/i.php?/upload/2024/07/16/20240716104644-84377e99-me.jpg)
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Post by jasoninsd on Jul 17, 2024 8:23:59 GMT -5
jasoninsd I wasn't suggesting you were being coy. I was trying to buck up your confidence. I started out cutting opal many years ago. I was poor. I remember waiting anxiously 3 months for 1 ounce of rough from Oz because it was shipped by sea mail and I couldn't afford air postage. I've been through many twists and turns with the lovely stuff since. I've experienced the same feelings you're going through many times. And still! Here are some images of the frustrating piece of Koroit rough I mentioned earlier in the thread. I think I've finally come up with a slabbing strategy but I'm almost afraid to try it for fear of messing up an irreplaceable natural creation. But that's opal cutting! Side View ![](https://rockshow.rocktumblinghobby.com/i.php?/upload/2024/07/16/20240716104429-1574b23d-me.jpg) Long Top View ![](https://rockshow.rocktumblinghobby.com/i.php?/upload/2024/07/16/20240716104558-f6656282-me.jpg) Close Top View ![](https://rockshow.rocktumblinghobby.com/i.php?/upload/2024/07/16/20240716104644-84377e99-me.jpg) I don't know how many times I've suffered from "paralysis due to over-analysis"! ![;)](//storage.proboards.com/forum/images/smiley/wink.png) I can see why you've pondered on that piece! My gosh you're not blowing smoke about "irreplaceable natural creation"! That is stunning...and you're going to get some amazing pieces out of that one! Quite often when I'm cutting, I ponder...in my own feeble way...what the universe went through...and the countless millennia it took for the piece of material to be created the way it was and finally land in my hands. Then I quite often wonder if I'm doing it justice...or a disservice by altering what nature made. Then...most of the time...I just cut and grind the heck out of it and hope for the best! LOL
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Post by hummingbirdstones on Jul 17, 2024 22:23:13 GMT -5
Jason just grind off all the gnarly and thin bits. Then cut your cab. Opals are notorious for being free forms. You're not going to be grinding anything really valuable off. Trust your instincts, grasshopper.
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