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
wampidy: Better stay away from those higher rocks mr.mohs cause they kin fall an kilt ya.
May 19, 2015 23:21:04 GMT -5
mr.mohs: only way to go-- Rock In Peace (or Pieces) ...mostly™
May 20, 2015 10:04:40 GMT -5
mr.mohs: Rock Roll Rehab
May 20, 2015 10:05:14 GMT -5
Fossilman: No rehab for me!!!!!! I love this addiction.......LOL
May 20, 2015 13:48:46 GMT -5
drocknut: No rehab or twelve steps forme either. Hello, I'm drocknut and I'm a proud rock addict
May 20, 2015 15:23:19 GMT -5
rockpickerforever: Embrace your addictions. They are what makes you special! I wonder, is rock hoarding a genetic or learned behavior?
May 20, 2015 16:18:49 GMT -5
mr.mohs: Rock Roll Revival !
May 20, 2015 16:40:34 GMT -5
150FromFundy: One more question ... If you are a confessed rock hound, are you a hunter, or a gatherer? Maybe we need an anthropologist on board to answer the tough questions.
May 20, 2015 17:31:57 GMT -5
drocknut: Both Jean. Also both hunter and gatherer.
May 20, 2015 21:54:34 GMT -5
wampidy: Rock thief is more like it. hahahaha
May 20, 2015 22:31:50 GMT -5
drocknut: Haha Jim, never gonna give that up are you?
May 20, 2015 22:34:39 GMT -5
rockpickerforever: Thanks for the smile, guys! Ah, memories...
May 20, 2015 23:10:19 GMT -5
jakesrocks: Neither hoarding nor genetic Jean. Rocks are fossilized rabbits, and just seem to multiply just like live rabbits. (Ever wonder what all of those little chips in the bottom of a box of rocks were)?
May 21, 2015 9:53:50 GMT -5