Novembr 16-18—COLUMBIA, SOUTH CAROLINA: Annual show; The Columbia, SC Gem and Mineral Society; Fri. 10-6, Sat. 10-6, Sun. 12-5
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 Post subject: Lapidary polishing help
PostPosted: Wed Nov 07, 2018 9:17 pm 
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This may not be the best place for this question but since I've made an account on here I figured I'd see if anyone has any helpful advice for me. I've been trying to polish the Ethiopian shewa opals as specimens. I'm having trouble when I get to the finer grits of my diamond wheels; the rhyolite shell around the opal is sometimes porous and sandy and I'll get scratches across the opal where the bits have come off. With some luck and careful manipulation of the piece I can get a good 3000 polish (from soft resin diamond wheel) on these, but I am certain if I tried to go to polish pad it would be disastrous, and would contaminate. This has happened when I've tried to polish cabs too (variscite comes to mind), if there are any "sandy" spots or veins in the material.

Is there some special technique to keep the bits from getting dislodged? Would covering the stone in superglue (and putting it in acetone later to remove) keep the sand in place or would pieces likely come off anyway? The stones look pretty good at 3k but I wanted to know if there was a trick, at least to know in the future.

Thanks!


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 Post subject: Re: Lapidary polishing help
PostPosted: Thu Nov 08, 2018 11:07 pm 
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I have certainly heard of people temporarily sealing stones with superglue, though removing it from an opal may be harder than an agate.
In these cases I generally just go very carefully to avoid those areas where possible. Hand-polishing it for the last stage might help as well.


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 Post subject: Re: Lapidary polishing help
PostPosted: Fri Nov 09, 2018 10:21 pm 
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Thanks, I might try to hand polish my better pieces. It's hard not to go over the problem areas with the wheels because I want to get at the opal adjacent to the rhyolite. I can see a difference in the finish around the edges if I don't.


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