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.
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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: My area got hit hard w/rain! But thru the genius of the Hohokam Indians, the grade of land caused all that water to bypass the homes & flow into the Salt River...mostly
Sept 9, 2014 16:42:49 GMT -5
Shotgunner: I hit a "pre-estate" sale today. Dude ain't dead yet. Saving his descendants the headache. Look for some cool sh\t. wampidy PM coming.
Sept 9, 2014 20:50:01 GMT -5
RocknCritter: Nice write up with lot's of good info. Another way to consider Depth of Field is "the amount of focus depth".. Lower aperture numbers mean less area. Higher numbers equal more. Also a change in focal length will alter the amount of DOF. With identical aper
Sept 10, 2014 6:27:22 GMT -5
Fossilman: Geoff,I use to sell scrap metal in North Dakota,before moving to Oregon....Did pretty good for just scrapping..Thumbs up
Sept 11, 2014 8:40:35 GMT -5
nowyo: Woo hoo! We got us a couple inches of global warming overnight!
Sept 11, 2014 9:22:11 GMT -5
rockpickerforever: Russ, could you send some of that this way? Could use it about now... Right now I'm looking forward to the next mini ice age.
Sept 11, 2014 14:52:05 GMT -5
rockpickerforever: Woo hoo! Finally! 4000 posts for wampidy! (Do you feel different now?) What an accomplishment, you can go take a nap now EDIT - You are so right, Jim, didn't mean to slight you. I fixed it. Must be the heat...
Sept 11, 2014 15:42:47 GMT -5
wampidy: hahahaha I just noticed that and came here to comment. I just feel older like when I turned 90. Nap sounds good but I have a lot of projects going now so it will have to be a short nap.
Sept 11, 2014 15:50:29 GMT -5
Fossilman: Well Jim,if you can't finish that nap,I'll nap a bit longer,so that might help ya' out...LMAO
Sept 11, 2014 16:05:52 GMT -5
wampidy: Hah Jean, you missed a zero and I just checked yours. You only have me beat by 136. Have you been slacking?
Sept 11, 2014 16:11:31 GMT -5
Shotgunner: Nothing better than the sound of the slab going 'clunk' at at the same moment the saw shuts off.
Sept 11, 2014 21:21:31 GMT -5
Geoff: Thanks for trying to keep the heat off me everyone
Sept 11, 2014 22:13:10 GMT -5
wampidy: Well dude, you are not forgettable and would hate to see a great father torn away from his beautiful babies so he could do hard time or community service. Plus you post some cool s..t. How are the babies by the way? When I see your name on here it reminds
Sept 12, 2014 8:26:06 GMT -5
wampidy: me of the photo of you and your daughter at the flat lap polishing rocks. Best photo of the decade.
Sept 12, 2014 8:27:02 GMT -5
Geoff: Those kids are obscene with their cuteness. Makes me want to throw up. :p
Sept 13, 2014 16:31:15 GMT -5
broseph82: Met a lady at my kids baseball game who is a former rockhound from Washington state. She said she had a bucket full of Adventurine that she would let me pick my fill from.
Sept 14, 2014 16:20:22 GMT -5