brent
fully equipped rock polisher
Member since November 2008
Posts: 1,316
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Post by brent on Dec 6, 2009 17:59:34 GMT -5
Well, I just took a batch out of the polish stage. I have a whole 14 stones that took a polish. The rest were dull and edges and point were beat up.
It was a batch of obsidian, soft jaspers, and some tiger eye. A couple of the tiger eye turned out ok, the rest were damaged. A goldstone turned out and a couple small mahogany obsidian.
I used rubber pellets and ran it for a week. I put the batch back in and added new polish. It's been so frustrating to tumble in a 6 pound tumbler for over a year and end up with less than two cups of finished stones.
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Sabre52
Cave Dweller 
Me and my gal, Rosie
Member since August 2005
Posts: 20,497
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Post by Sabre52 on Dec 6, 2009 18:30:27 GMT -5
Dang Brent that's rough. Three things that might help. Tumble the stones in coarse until they have very smooth rounded contours. It's the edges that do a lot of chipping and bruising. Add a really large percentage of small stones to the load to increase surface to surface contact and prevent the larger stones from dropping on each other and bashing around so much. Finally, in the two grind stages, add old slurry to thicken the mix so the stones don't move around and bash into each other with as much speed. In the fine grind, use plastic pellets with the thicker slurry and check for chips, abrasions, impact fractures etc at the end of the two grind phases making sure the stones are smooth before you move them on, as prepolish and polish will do nothing to erase this sort of damage.....Mel
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tomcloss
starting to spend too much on rocks
Member since October 2008
Posts: 158
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Post by tomcloss on Dec 6, 2009 18:35:38 GMT -5
Not sure if this was a problem with your batch but I thought Obsidian was softer then Tiger Eye. Usually I tumble obsidian and apache tears by themselves.
Just my :2cents:
Tom
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brent
fully equipped rock polisher
Member since November 2008
Posts: 1,316
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Post by brent on Dec 6, 2009 19:11:51 GMT -5
It's always in the final polish were they get banged up. Maybe my slurry is too thin? I put them back in with more pellets, less water and more fresh polish.
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Post by johnjsgems on Dec 6, 2009 22:22:47 GMT -5
If a rotary you would do better running the obsidian separate from the jasper and tiger eye. Not sure what "soft jasper" is but I'm guessing you will be disappointed polishing it.
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MikeS
fully equipped rock polisher
Member since January 2009
Posts: 1,081
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Post by MikeS on Dec 6, 2009 22:34:17 GMT -5
Agreed...the mixture of soft and hard is probably your problem here. A question...was one type of material or materials more beat up than the other ones? if so, which ones?
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brent
fully equipped rock polisher
Member since November 2008
Posts: 1,316
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Post by brent on Dec 6, 2009 23:15:02 GMT -5
Scrooge, some tiger eye was beat up a couple pieces were nice. A couple small pieces of obsidian were nice, the rest were not shiny. The jasper has come out shiny in other batches, but not this time.
It makes no sense to me. The one batch that turned out good had a mix of all stones. now I take out the agates and things don't work like they did before. I think I'll have to run with one type of rock in each batch. Or, just scrap everything and start over.
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Post by susand24224 on Dec 7, 2009 0:05:21 GMT -5
With obsidian, I usually use cerium oxide polish. On the last batch, though, I decided to try aluminum oxide polish. It worked--but not for three weeks. Perhaps a bit longer would help?
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brent
fully equipped rock polisher
Member since November 2008
Posts: 1,316
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Post by brent on Dec 7, 2009 7:41:55 GMT -5
AO is what comes with the tumbler kits? I do have cerium. Can try that next time.
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montezuma
off to a rocking start
Member since December 2009
Posts: 21
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Post by montezuma on Dec 7, 2009 9:16:47 GMT -5
This comment is not from actually doing tumbling yet, but from the hints I've read. Did you add enough pellets to soften the blows?
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Post by johnjsgems on Dec 7, 2009 12:04:07 GMT -5
Al Ox in the kits is usually a 3-4 micron that will work well in rotaries on harder stones and sometimes in vibes. The finer Al Ox (sub micron, .5 or .3 micron) will work better on a wider range of hardness in a vibe (or buffing wheel). Cerium has been the standard for both obsidian and the agates and jaspers. Many old timers ran obsidian in cerium in Karo syrup. I've cabbed tiger eye and although it is hard it likes to break at a "fiber line" at last minute. If that happens in the tumbler you would have a hard, sharp surface rotating in the load.
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Post by johnjsgems on Dec 7, 2009 12:07:42 GMT -5
By the way, many tumbling kits use "CPP" polish rather than Al Ox. It has mixed results. Most that like it use a lot of it compared to more expensive polish.
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brent
fully equipped rock polisher
Member since November 2008
Posts: 1,316
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Post by brent on Dec 7, 2009 16:32:14 GMT -5
John, could it be that it is the tiger eye causing the problem? The one batch that worked out didn't have any tiger eye.
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Post by johnjsgems on Dec 7, 2009 20:49:19 GMT -5
The "beat up" tiger eye could have broken up and the pieces caused the problems. Tiger eye is an agate replacement of asbestos so very hard and should not be mixed with obsidian and softer material.
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Post by tkrueger3 on Dec 7, 2009 21:09:00 GMT -5
I just had some really good results with obsidian in a rotary using M-5 polish bought off eBay. Only one week in final polish did the trick.
Tom
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MikeS
fully equipped rock polisher
Member since January 2009
Posts: 1,081
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Post by MikeS on Dec 7, 2009 21:33:54 GMT -5
could you post some photos of the damaged stones?
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