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Post by perkins17 on Jul 28, 2021 11:21:20 GMT -5
I self collected some common opal that (hopefully) isn't crazed. I did my best to find the most solid prices and now want to tumble some. I had some obsidian laying around that I broke up and added in with the opal. Does anyone have any tips on how best to tumble these two? Thanks!
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Post by manofglass on Jul 28, 2021 11:31:40 GMT -5
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Post by perkins17 on Jul 28, 2021 11:57:06 GMT -5
Thanks. I'll read through those now.
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Post by hummingbirdstones on Jul 28, 2021 21:12:20 GMT -5
Your common opal should be ok. It generally does not craze.
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Post by perkins17 on Jul 28, 2021 21:28:23 GMT -5
Thanks hummingbirdstones I had trouble with my first tumble of it. very flaky fragile material. Might have to use a ton of ceremics
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Post by hummingbirdstones on Jul 29, 2021 9:19:11 GMT -5
Thanks hummingbirdstones I had trouble with my first tumble of it. very flaky fragile material. Might have to use a ton of ceremics Opal is amorphous, like glass, and can be brittle. Lots of cushioning, I would think. I don't tumble, but you can look at some of jamesp's glass tumbling threads.
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,561
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Post by jamesp on Jul 31, 2021 3:04:30 GMT -5
Never tried opal. It is a good chance that the more hard silica content the better.
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Post by perkins17 on Jul 31, 2021 8:52:29 GMT -5
It is kind of interesting because some of it is slightly translucent and would look great shiny. Last time I tumbled it I ended up with a can of opal chips because it was so crazed and brittle. This time around, I tried to pick the least brittle prices to tumble.
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Post by hummingbirdstones on Jul 31, 2021 9:36:47 GMT -5
I don't tumble, but I have cut a ton of opal in my time. Some opal is going to craze no matter what you do. It has to do with the amount of water in the opal. The more water in it, the more the chance of it crazing as it dries out. Also, opal forms under pressure. Cutting or tumbling it can release the stress and also cause it to craze.
I would think (but don't know for sure) that rotary tumbling is going to be really hard on it unless you have lots of cushioning and a thickener in there. It probably would do better in a vibe, but I would err on the side of caution and also use lots of cushioning and a thickener.
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rewdownunder
spending too much on rocks
Member since March 2012
Posts: 357
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Post by rewdownunder on Jul 31, 2021 15:03:58 GMT -5
A friend of mine who mines opal in Australia puts lower grade material out in the sun for several months then tumbles what holds up for school kids. Poor material will fall apart in the dry hot sun and the solid stuff will last. He claims there is no way to tell by looking at it what will tumble and what will not. It sounds like it is more the function of the material rather than your method.
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Post by perkins17 on Jul 31, 2021 23:37:32 GMT -5
Thanks! I might get it up and running in about a month with the opal.
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Post by hummingbirdstones2 on Aug 1, 2021 9:12:04 GMT -5
A friend of mine who mines opal in Australia puts lower grade material out in the sun for several months then tumbles what holds up for school kids. Poor material will fall apart in the dry hot sun and the solid stuff will last. He claims there is no way to tell by looking at it what will tumble and what will not. It sounds like it is more the function of the material rather than your method. Good tip there from down under.
One of the old-time miners in Virgin Valley used the same "sorting" process. He would put his rough on a metal roof for the summer. Any pieces that were solid at the end of the season could be cut into cabs.
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