Mike I am new at rock tumbling also. I have Petoskey stones also. I read that since they are a soft stone you have to be real careful. The book told how to polish by hand. I tumbled mine for about 24 hrs. I used a medium grit. By looking at them, I am afraid to put them back in the tumbler with the polish compound. My plan is just spray them with lacquer. I haven't done it yet. Hope this helps. I am sure someone who has more knowledge and maybe has tumbled Petoskey stones would have more info then me.
I also have what you call 'soft Petoskey stones'. I know those cannot go in the tumbler or be hand polished. The book tells me just to put them in a pretty jar with some mineral oil. I was thinking about trying to spray just one of them with the lacquer and see what happens.
Mike, petrosky stone, as far as I know is a calcite. The coral it originates from has not gone mineral transfer. Of the few petrosky stones I have tumbled, I have so degraded the stone with all the polishes I was left with very little. A stone polisher I know, saves the final polish for the petosky stones after he cabs the original shape. He routinely mass final polished all his cabs I have never been able to final polish my cabs so I use a leather buff and cerium or tin oxide. I suggest if you have some choice samples, put them aside. Larimar is also similar. Do not tumble Larimar. If the only way I could polish petrosky stone was to tumble, I would do 220 for a few days, checking constantly. I would move up to 660 for a week, and run at least two weeks with cerium oxide. There might be some non mineralized organics trapped in the centers of the coral cells. Watch for gas build up. I once tumbled some fossilized buffalo scat and the tumbler had a soupy green mixture. There was no odor, but I suspect the mineralization was incomplete deep into the stones. It leached out with the tumble. Just my perspective on this. I often wondered if the reason the petrosky stone is localized to the Great Lakes region and not near ocean shores is the wave activity and the softness of the stone. If some seem agatized tumbling might work. Just keep a watch on it.
In the beginning was the Floyd, and the Floyd was with Him, and He was with the Floyd. Syd Barret just disappeared, right after the happening. Lita Ford drives a suburban! Big Hair Heavy Metal is dead. Oh weeping and gnashing of teeth, the end is near. The answer is 42. 42! BING! BIG BING!
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:)hello its mike i just started my pre polish on my petoskey stones i did what you all said and that seams to work fine i left them in 14 houres with 300 then went to 400 ...14h. then 600. 14h. not done yet but they sure look prety good.... ;D thanks for all the help. ......mike
mr.mohs: got busted for jay walking in Vegas... ...so I knew wouldn't have any luck gambling...mostly™
Aug 26, 2015 17:57:33 GMT -5
Fossilman: I was with a buddy that didn't have a brain! He stole a "Hookers" purse!! Told him not too,wouldn't be anything in it...Hey guess what,there wasn't anything in it!!! Glad I was underage! He wasn't!! They kind of rough him up a bit ......
Aug 27, 2015 9:11:28 GMT -5
Fossilman: The cops told me I should lose the bum,I guess he had a pretty good wrap sheet going in Cali and Montana...Went our different ways in Salt Lake City,Utah...
Aug 27, 2015 9:12:53 GMT -5
mr.mohs: your buddy took the line from the j.geils song to literally--- first I look at the purse
Aug 27, 2015 9:45:14 GMT -5
gemsgalore: I need some advice for tumbling my first opal. It's 2"w x 1-1/2"h, circumference is 4-1/2". I only have ceramic filler but no grinding grit on hand. Can I tumble without the grit?
Aug 27, 2015 10:22:46 GMT -5
jakesrocks: gemsgalore, please post your question here. http://andy321.proboards.com/board/22/totally-rock-tumbling
Aug 27, 2015 10:50:32 GMT -5
Fossilman: Ed-exactly!!! He seen the purse,told he was going to take it..I called him a moron and he proved to me,that I was right..I was 15,he was 23...
Aug 27, 2015 11:50:07 GMT -5
mr.mohs: gemsgalore-- I got better idea of what to do with that chunk of opal. Rather than put it in a barrel------- hand polish it with 37,000gr emery paper and save it as a specimen...mostly
Aug 27, 2015 17:15:54 GMT -5
dhotrocknut: Mike at least ya have an interesting tale to tell out of that mess.lol
Aug 28, 2015 18:24:51 GMT -5
dhotrocknut: FYI I'm no longer in Nevada and am going to get dinner and desert. I'll have to let you all know if it was worth the trip.
Aug 28, 2015 18:28:07 GMT -5
mr.mohs: get some sherbet ice cream for desert, diane.... that will cool you down... mostly
Aug 28, 2015 18:46:33 GMT -5
mikeyrocks: Hey ms D you on your way to S Cal? Safe travels
Aug 28, 2015 19:31:31 GMT -5
parfive: September Rock & Gem, coupla familiars on p29.
Aug 28, 2015 19:34:38 GMT -5
quartz: 1 1/2 hrs. steady rain this A.M., first since mid May. Thanks to all for doing your rain dances.
Aug 29, 2015 7:25:47 GMT -5
Fossilman: Yes Diana,there is more to that story too..LOL We received some good rain lastnite too,more coming this week...Los of thunder,liking that!
Aug 29, 2015 9:28:58 GMT -5