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!
Follow the White Rabbit!
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: Crisp hot whiteness-City Noon-Occupants of Rock Zone are Consumed (Santa Ana are winds off the desert) jdmostly
Mar 26, 2015 10:05:57 GMT -5
drocknut: Oh Jean hope you didn't put away your long undies for those kinds of temps...lol. lol Ed.
Mar 26, 2015 10:10:21 GMT -5
headfullofrocks: Aaaahhhhh, Vancouver Island, Appx. 13deg Celsius. Grass is green, got some obsidian in cerium oxide tumbling away, and the sun is peeking through the clouds, can't ask for much better in the lap of geographical luxury. :
Mar 26, 2015 14:55:57 GMT -5
Shotgunner: Mike, we harvested potatoes a few weeks ago!
Mar 27, 2015 20:15:13 GMT -5
meviva: Anyone going to the Anthem, AZ show tomorrow?
Mar 27, 2015 22:42:48 GMT -5
mr.mohs: so Anthem tomorrow? I went last year. I'll keep it in mind
Mar 27, 2015 23:06:05 GMT -5
Shotgunner: They are promising 94 today!
Mar 28, 2015 9:31:36 GMT -5
Fossilman: Scott,do you have a greenhouse or what?? Or just warm enough temps in the winter months..Can't beat fresh spuds!!!
Mar 28, 2015 9:42:34 GMT -5
drocknut: I like fresh spuds too. Hard to grow anything in a travel trailer though. Yikes, 94 is way too hot. They are talking close to 90 here at my mom's so I may be hiding in the ac for a while.
Mar 28, 2015 11:06:36 GMT -5
mr.mohs: yep- the southwest got ripped off this season-- High pressure everywhere... was thinking of going to anthem...but it to hot for the trek. no a.c. & the freeze plug is weak...
Mar 28, 2015 11:16:56 GMT -5
drocknut: Does not bode well for the summer ed
Mar 28, 2015 11:37:17 GMT -5
mr.mohs: it would seem that way. Diane. BUT I recall one unseasonably warm spring and yet we had a mild summer. the last couple summers have been mild --although this last summer -- lasted all winter & spring UUUGHH! Maybe in for brutal one...
Mar 28, 2015 12:39:11 GMT -5
Fossilman: Helping Tammy can grapefruit today...................Juice and fruit...LOL,she loves it,I hate the stuff..
Mar 28, 2015 15:48:30 GMT -5
drocknut: I hope it's not a brutal one Ed.
Mar 29, 2015 1:33:45 GMT -5
snowmom: fossilman, I'm with Tammy. that's good stuff! Grapefruit juice is my favorite drink.
Mar 29, 2015 9:53:25 GMT -5
drocknut: I don't care for grapefruit juice, too bitter for me even with a lot of sugar added.
Mar 29, 2015 16:43:28 GMT -5
Fossilman: I couldn't drink it even if I did like it-bad reaction with my meds and grapefruit juice...
Mar 29, 2015 17:14:26 GMT -5
drocknut: I understand that, grapefruit juice does not mix well with lots of meds.
Mar 29, 2015 17:41:38 GMT -5
lparker: It does mix well with Black Velvet
Mar 29, 2015 18:42:42 GMT -5
Shotgunner: Mike, winter is the season to grow potatos in SoCal. Lettuce greens too. Tomatoes are a perennial here. Plant once and harvest for years. Just cut back the plants at the end of winter for new growth in spring.
Mar 29, 2015 18:53:48 GMT -5