Rubykicks Posted May 13, 2021 Share Posted May 13, 2021 I found this lovely rock at the Monroe reservoir on Monday. I believe it's a petosky stone, but maybe I'm wrong. I'm also wondering if I should try to polish it or anything or if it would be best left alone. 1 Link to comment Share on other sites More sharing options...
fossilhunter21 Posted May 13, 2021 Share Posted May 13, 2021 (edited) To me it doesn't look like a petoskey, but I am no expert on coral. Edited May 13, 2021 by fossilhunter21 Link to comment Share on other sites More sharing options...
Lone Hunter Posted May 13, 2021 Share Posted May 13, 2021 I believe I see the rugose coral that would be in a Petoskey stone, the difference being it's not a small peice that has rounded off into the typical shape of one. I could be wrong so wait for another opinion! Link to comment Share on other sites More sharing options...
Rubykicks Posted May 13, 2021 Author Share Posted May 13, 2021 Let me see if I can adjust the brighntess on the 5th picture. You cab see the more defined pattern there. Link to comment Share on other sites More sharing options...
Rubykicks Posted May 13, 2021 Author Share Posted May 13, 2021 Tell me if these adjustments work. If not, i'll just take a new picture. I wasn't aware petosky stones had to be rounded so it may not be. Link to comment Share on other sites More sharing options...
Thomas.Dodson Posted May 13, 2021 Share Posted May 13, 2021 Petoskey stones are generally called as such because they're from that area in Michigan. The actual genera usually defined as Petoskey stones is the coral Hexagonaria. This looks like some other colonial rugose coral to me. Have you checked a geologic map of the area yet? I think it looks nice as is and you would hard pressed to polish it since none of the surfaces are flat or smooth. Some people would consider slicing it with a rock saw and polishing that but that is up to your preference. If it were me I'd leave it as is or just maybe cut a small piece to polish that isn't on a display side. 2 Link to comment Share on other sites More sharing options...
Fossildude19 Posted May 13, 2021 Share Posted May 13, 2021 Some sort of coral for sure. Would probably polish up nicely. Tim - VETERAN SHALE SPLITTER VFOTM --- APRIL - 2015 __________________________________________________ "In every walk with nature one receives far more than he seeks." John Muir ~ ~ ~ ~ ><))))( *> About Me Link to comment Share on other sites More sharing options...
fossilhunter21 Posted May 13, 2021 Share Posted May 13, 2021 (edited) Hexagonaria percarinata (the coral that petoskeys are made of) have six sided walls, see image below. If your coral does not have six walls it is not a petoskey stone. But fossil coral can still be Hexagonaria percarinata even when it is not a petoskey stone, and Hexagonaria percarinata can still have have six walls without being a petoskey stone. Edited May 13, 2021 by fossilhunter21 1 Link to comment Share on other sites More sharing options...
Rubykicks Posted May 13, 2021 Author Share Posted May 13, 2021 1 hour ago, Thomas.Dodson said: Petoskey stones are generally called as such because they're from that area in Michigan. The actual genera usually defined as Petoskey stones is the coral Hexagonaria. This looks like some other colonial rugose coral to me. Have you checked a geologic map of the area yet? I think it looks nice as is and you would hard pressed to polish it since none of the surfaces are flat or smooth. Some people would consider slicing it with a rock saw and polishing that but that is up to your preference. If it were me I'd leave it as is or just maybe cut a small piece to polish that isn't on a display side. I have looked to find the coral from tue area, but I haven't found anything that matches. I may be looking in the wrong places. Link to comment Share on other sites More sharing options...
Thomas.Dodson Posted May 13, 2021 Share Posted May 13, 2021 Was this specimen found among bedrock? Almost all of the area of Monroe Reservoir is outcrops of the Edwardsville Formation of the Borden Group (Mississippian). I see some decent studies on the formation on google. If it was found as "float" material though you can't rule out the possibility of relic material from older formations or wash ins. I certainly saw a lot of this in corals in river basins in Illinois where large chunks of Hexagonaria were common. Incidentally, as a word of caution, most of the public land around Monroe Reservoir is closed to fossil collecting. There is a designated collection pile in Paynetown State Recreation Area though. https://www.gosoin.com/ohio-valley-fossil-trail/monroe-lake/ That's more than most places get. 1 Link to comment Share on other sites More sharing options...
Rubykicks Posted May 13, 2021 Author Share Posted May 13, 2021 So, really, it's Hexagonoria, but simply isn't called petosky or petoskey because it wasn't found in Michigan? I see nothing else online that looks like this. I was surprised when I saw it because I knew they were usually only found in Michigan. I don't know what kind of rock it was in, but it seems like there was a lot of quartz. I'm not super familiar with the different types of minerals though. Link to comment Share on other sites More sharing options...
Kane Posted May 13, 2021 Share Posted May 13, 2021 1 minute ago, Rubykicks said: So, really, it's Hexagonoria, but simply isn't called petosky or petoskey because it wasn't found in Michigan? I see nothing else online that looks like this. I was surprised when I saw it because I knew they were usually only found in Michigan. I don't know what kind of rock it was in, but it seems like there was a lot of quartz. I'm not super familiar with the different types of minerals though. Petoskey stone is a colloquial term, not a scientific one. Also, I would guess the crystallization is calcite and not quartz. You can test that with vinegar (if it fizzes, then calcite) 1 ...How to Philosophize with a Hammer Link to comment Share on other sites More sharing options...
LabRatKing Posted May 13, 2021 Share Posted May 13, 2021 8 minutes ago, Rubykicks said: So, really, it's Hexagonoria, but simply isn't called petosky or petoskey because it wasn't found in Michigan? I see nothing else online that looks like this. I was surprised when I saw it because I knew they were usually only found in Michigan. I don't know what kind of rock it was in, but it seems like there was a lot of quartz. I'm not super familiar with the different types of minerals though. Yep. The colloquial terminology only applies to hexagonoria from the area that has been naturally tumbled and polished by the lake. I agree this is hexagonororia, and in my mind should be classified as “proto-petrovski”. Right source, just lacking the natural action. 1 Link to comment Share on other sites More sharing options...
piranha Posted May 13, 2021 Share Posted May 13, 2021 Acrocyathus is the abundant colonial coral in the Mississippian of Indiana. This monograph has similar species/subspecies of A. floriformis (w/polygonal corallites). Sando, W.J. 1983 Revision of Lithostrotionella (Coelenterata, Rugosa) from the Carboniferous and Permian. United States Geological Survey, Professional Paper, 1247:1-52 PDF LINK 4 1 Link to comment Share on other sites More sharing options...
Thomas.Dodson Posted May 13, 2021 Share Posted May 13, 2021 1 hour ago, Rubykicks said: So, really, it's Hexagonoria, but simply isn't called petosky or petoskey because it wasn't found in Michigan? I see nothing else online that looks like this. I was surprised when I saw it because I knew they were usually only found in Michigan. I don't know what kind of rock it was in, but it seems like there was a lot of quartz. I'm not super familiar with the different types of minerals though. Yes, as Kane mentioned Petosky stones are a colloquial term. As an example, Hexagonaria I find in Illinois are simply Hexagonaria. I still don't personally think this is Hexagonaria based on my experience (albeit limited). I'll ask again if you think this came from an outcrop at the site because Hexagonaria is limited to the Devonian and the outcrops at Lake Monroe are all Mississippian. Was the rock surrounding the area of the same type as this specimen? If you can pinpoint origin we can likely rule out Hexagonaria immediately. There are other corals with polygonal corralites that are similar to Hexagonaria. I think Piranha is closer with Acrocyathus. 1 1 Link to comment Share on other sites More sharing options...
FossilNerd Posted May 13, 2021 Share Posted May 13, 2021 52 minutes ago, piranha said: Acrocyathus is the abundant colonial coral in the Mississippian of Indiana. This monograph has similar species/subspecies of A. floriformis (w/polygonal corallites). Sando, W.J. 1983 Revision of Lithostrotionella (Coelenterata, Rugosa) from the Carboniferous and Permian. United States Geological Survey, Professional Paper, 1247:1-52 PDF LINK Dang! You beat me to it Scott! And I knew this one too. Oh well... I’ll have to be quicker on the draw next time. Until then, I agree! The good thing about science is that it's true whether or not you believe in it. -Neil deGrasse Tyson Everyone you will ever meet knows something you don't. -Bill Nye (The Science Guy) Link to comment Share on other sites More sharing options...
piranha Posted May 14, 2021 Share Posted May 14, 2021 5 minutes ago, FossilNerd said: Dang! You beat me to it Scott! And I knew this one too. Oh well... I’ll have to be quicker on the draw next time... These always work well for me: 1 Link to comment Share on other sites More sharing options...
Rubykicks Posted May 14, 2021 Author Share Posted May 14, 2021 Yes, it matched the other rock... Link to comment Share on other sites More sharing options...
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