jlcochran42
starting to shine!
Member since July 2020
Posts: 29
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Post by jlcochran42 on Aug 16, 2020 11:31:40 GMT -5
Hello all...I'm thinking about tumbling some Opal as a gift for my wife and make a piece of jewelry out of it. I hear Opal is pretty soft and has a tendency to crack.
I want to know if anyone has had any success with tumbling Opal and if you have any advice.
Thanks in advance.
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braat
spending too much on rocks
Member since December 2016
Posts: 350
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Post by braat on Aug 16, 2020 11:55:07 GMT -5
Never tumbled opal so can't offer anything but if you Google search the RTH forum for answers using the box just above your post you'll get lots of info...
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Post by knave on Aug 16, 2020 12:52:05 GMT -5
I assume you’re speaking of opal potch, not precious opal. It should take a very nice shine but be gentle with it like you said.
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lordsorril
freely admits to licking rocks
Member since April 2020
Posts: 866
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Post by lordsorril on Aug 16, 2020 13:25:33 GMT -5
I've only tumbled African Rough Green Opal. My experience is that it tends to shatter at every step of the process. As such it needs cushioning at every stage and especially at polish. Not easy to get a large finished piece, but, relatively easy to get smaller ones.
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jlcochran42
starting to shine!
Member since July 2020
Posts: 29
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Post by jlcochran42 on Aug 16, 2020 14:44:17 GMT -5
I've only tumbled African Rough Green Opal. My experience is that it tends to shatter at every step of the process. As such it needs cushioning at every stage and especially at polish. Not easy to get a large finished piece, but, relatively easy to get smaller ones. Is there a specific type of cushioning you recommend?
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lordsorril
freely admits to licking rocks
Member since April 2020
Posts: 866
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Post by lordsorril on Aug 16, 2020 15:03:39 GMT -5
I've only tumbled African Rough Green Opal. My experience is that it tends to shatter at every step of the process. As such it needs cushioning at every stage and especially at polish. Not easy to get a large finished piece, but, relatively easy to get smaller ones. Is there a specific type of cushioning you recommend? I used plastic pellets at each stage. 3lb. Barrel about 1/2 full with rough, and then topped off to 3/4 full with plastic pellets. Note: I had to separate the Silicon Carbide exposed plastic pellets from each stage from the Aluminum Oxide ones as the SiC seems to embed. Stage 1 for me was three weeks @120 grit Silicon Carbide. It was a slow process because the pellets impede the grinding, but, it is better than fragmenting. I also cut back on the amount of SiC and AOx I added to the barrels as well--plastic pellets will really slow down the action. Of course I did ruin a pound or two of material before I got this process right--I use a Lortone 33B as a tester for small batches of new material. I don't think I would use this material in a larger tumbler without seriously tinkering with the slurry consistency.
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Post by pauls on Aug 16, 2020 17:00:06 GMT -5
It comes up quite nice, I have tumbled it just in with everything in the rotary. Mainly potch but a few pieces with a thin vein of nice stuff running through it. It's harder and tougher than you would imagine. You are probably better to do it in the vibe though. Keep an eye on it.
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jlcochran42
starting to shine!
Member since July 2020
Posts: 29
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Post by jlcochran42 on Aug 16, 2020 22:04:39 GMT -5
It comes up quite nice, I have tumbled it just in with everything in the rotary. Mainly potch but a few pieces with a thin vein of nice stuff running through it. It's harder and tougher than you would imagine. You are probably better to do it in the vibe though. Keep an eye on it. I've read that it was best to use a vibrating tumbler. Looks like I will have to invest in one.
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jlcochran42
starting to shine!
Member since July 2020
Posts: 29
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Post by jlcochran42 on Aug 16, 2020 22:06:31 GMT -5
Is there a specific type of cushioning you recommend? I used plastic pellets at each stage. 3lb. Barrel about 1/2 full with rough, and then topped off to 3/4 full with plastic pellets. Note: I had to separate the Silicon Carbide exposed plastic pellets from each stage from the Aluminum Oxide ones as the SiC seems to embed. Stage 1 for me was three weeks @120 grit Silicon Carbide. It was a slow process because the pellets impede the grinding, but, it is better than fragmenting. I also cut back on the amount of SiC and AOx I added to the barrels as well--plastic pellets will really slow down the action. Of course I did ruin a pound or two of material before I got this process right--I use a Lortone 33B as a tester for small batches of new material. I don't think I would use this material in a larger tumbler without seriously tinkering with the slurry consistency. Do you know if ceramic cylinders work better?
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lordsorril
freely admits to licking rocks
Member since April 2020
Posts: 866
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Post by lordsorril on Aug 17, 2020 5:36:49 GMT -5
Short answer is: No-I don't know if ceramics work better. I have ceramics available, but, I have not run into a situation where I've needed to use them yet. I use pre-rounded quartz fish tank gravel: a 20lb bag is $20 ($1/lb) at Petco (vs. ceramic cylinders $4+/lb). Works great for me in rotaries and vibes. I have to knock off the edges on some of the pieces by sending them through a rough grind batch (with Mohs 7 material), but, easy going from there. Note: If you are going to use ceramics or gravel with lower mohs rocks like African Green Opal: I recommend you check your barrels frequently...I'm too busy to do that--I prefer once/week so I trust plastic pellets not to strike and fracture/scratch the material.
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gatorflash1
spending too much on rocks
Active in Delaware Mineralogical Society, Cabchon Grinding and Polishing, 2 Thumlers B's and a UV-18
Member since October 2018
Posts: 375
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Post by gatorflash1 on Aug 30, 2020 7:04:54 GMT -5
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Fossilman
Cave Dweller
Member since January 2009
Posts: 20,709
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Post by Fossilman on Aug 30, 2020 9:59:39 GMT -5
I have tumbled opal, it does crack and sometimes shatter, even with the media added... I do it all on a wheel now...
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