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Post by rmf on Jun 6, 2022 3:18:19 GMT -5
I know there are several on here that routinely work with Petoskey Stone(PS). I am looking for information.
1. I have found some PS to not have much contrast in color between the center and the outside of the cell. The light brown outer ring with a darker brown center gives more contrast and has more eye appeal. I have read of taking a vegetable oil with a low smoke temp and soaking the PS then gently heating in the oven until the oil smokes. The would then cause the center part to be darker.
A. Has anyone tried this? B. Is this normal practice for those who make $$ from selling PS cabs?
2. PS is composed mostly of calcite with some silica. This is similar to concrete. Has anyone played with using sodium silicate to harden the surface prior to polishing, similar to what is done with concrete prior to polishing?
TIA
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Post by Jugglerguy on Jun 6, 2022 11:57:04 GMT -5
I work with Petoskeys a lot but have never done either of these things. I have heard that vegetable oil goes bad, so I’d be worried that it would stink. If I tried soaking them, I’d use mineral oil. I have cut Petoskeys in mineral oil but have never noticed an improvement to the rock other than it looking like it’s wet.
I’m pretty choosy about the Petoskeys I pick up because of what you’re experiencing. I look for rocks with really good contrast. I’m lucky enough to live in a state where I can afford to be picky.
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Post by rmf on Jun 6, 2022 12:45:53 GMT -5
Jugglerguy Thanks for the info. I have another question for you since you list Alpena MI as location. I have heard that there are quarries there that have fossils that can be hunted. I heard this years ago when I was a kid and have never had the time to travel there to see if it is true. Any quarries that can be hunted?
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Post by rmf on Jun 6, 2022 12:57:32 GMT -5
One more thing. Thanks Jugglerguy for the info. I am assuming that if veg oil was used and heated to smoke the carbon would be left and the other stuff would be driven off so it should not go rancid. For treating stones to stabilize them they recommend treating with a degreaser first to remove saw oil which should also remove any remaining oil. recommendations for concrete polishing is prep surface a 400 grit before treating. That would mean undoping a stone and redoping so not convenient. right now it is a thought problem. Not sure if I want to experiment with it yet. |
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Post by Jugglerguy on Jun 6, 2022 22:26:11 GMT -5
Jugglerguy Thanks for the info. I have another question for you since you list Alpena MI as location. I have heard that there are quarries there that have fossils that can be hunted. I heard this years ago when I was a kid and have never had the time to travel there to see if it is true. Any quarries that can be hunted? The active quarries cannot be hunted, but Rockport is a state park and can be hunted. There are some huge Petoskey Stones there, but in my experience, they are not good for lapidary purposes. There are literally many tons of fossils there though. The quarry is fun, the beach is fun, and the sinkholes behind the quarry are fun too. Here's one of my videos of the quarry: I have other videos of the quarry, beach, and sinkholes. In fact, this Friday's video shows gastropods that my son in law and I found on the beach. |
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Post by rmf on Jun 7, 2022 13:47:32 GMT -5
Jugglerguy Yes, that is what I'm talking about. thanks for the info and the vid. I had a great uncle that collected brachiopods over there. They were nice, he did not know about the fish I am sure. I am thinking the oil in MI is all from the Devonian in sediments around the reef(s).
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Post by Jugglerguy on Jun 8, 2022 10:05:34 GMT -5
Jugglerguy Yes, that is what I'm talking about. thanks for the info and the vid. I had a great uncle that collected brachiopods over there. They were nice, he did not know about the fish I am sure. I am thinking the oil in MI is all from the Devonian in sediments around the reef(s). If you want brachiopods, I have better locations for those. If you ever decide to make a trip for fossils, let me know and I'll set you up with some good locations. |
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Post by rmf on Jun 8, 2022 15:43:46 GMT -5
Jugglerguy Yes, that is what I'm talking about. thanks for the info and the vid. I had a great uncle that collected brachiopods over there. They were nice, he did not know about the fish I am sure. I am thinking the oil in MI is all from the Devonian in sediments around the reef(s). If you want brachiopods, I have better locations for those. If you ever decide to make a trip for fossils, let me know and I'll set you up with some good locations. Thanks, John
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Post by chris1956 on Jul 20, 2022 21:06:54 GMT -5
I know there are several on here that routinely work with Petoskey Stone(PS). I am looking for information.
1. I have found some PS to not have much contrast in color between the center and the outside of the cell. The light brown outer ring with a darker brown center gives more contrast and has more eye appeal. I have read of taking a vegetable oil with a low smoke temp and soaking the PS then gently heating in the oven until the oil smokes. The would then cause the center part to be darker.
A. Has anyone tried this? B. Is this normal practice for those who make $$ from selling PS cabs?
2. PS is composed mostly of calcite with some silica. This is similar to concrete. Has anyone played with using sodium silicate to harden the surface prior to polishing, similar to what is done with concrete prior to polishing?
TIA
Sorry for the response time as I am new to the forum. I wouldn't use the vegetable oil as the organics may degrade with time. When I first started polishing Petoskey stones last year, I read somewhere (can't find it now) that you can make the stones darker by using mineral oil in an oven. You submerge the stone in the mineral oil and heat to 200 F for 2 hours. I have tried this several times with mixed results. It seems to make most stones darker but sometimes too dark and seems to dull the finish somewhat (I haven't tried buffing this out on a wheel afterwards yet). It does work well on making small cracks disappear although I tried oil after I had polished a stone (saw a crack after polishing) and it didn't make the crack disappear (may have filled the crack with small particles from polishing?). I am also not sure how long this will last. I have some that are about 6 months old and still look dark. I am not sure that this will work on a very light color rock. Also, any limestone areas on the rock will be very dark. The first time I tried this I did it in our kitchen oven and it left a funny after smell to the oven for several days. So you might want to get a small toaster oven that you can dedicate to rocks. Since I got the toaster oven, I haven't had that smell (maybe it was some organics in my first batch of rocks). You might try this on some not so good stones to start with and see how it works. |
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Post by rmf on Jul 21, 2022 18:43:24 GMT -5
chris1956 thanks for your input. I am doing some other experiments right now but may get back to the petoskey.
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