SteveR Posted July 19, 2021 Share Posted July 19, 2021 I found this along the Mississippi River at Alton IL, but it was in an area that's been extensively modified by dumping dredged rock and sand out of the barge channel onto the banks, which means it could be anything from any period. I've walked those banks for many years and occasionally found rounded black things with a cellular-looking pattern caused by shrinkage of the outer layer, but they're generally fairly soft and this is hard as, well, rock. Is that all it is, or could it be some kind of fossil? I've never found any kind of fossil there, so I have doubts. Mostly the fossils are from the Ordovician, and miles further north or southwest in different types of formations, but as I say this likely came from dredging in the river so it could have been washed down from anyplace upstream, which covers a lot of territory. So, rock or fossil? 1 Link to comment Share on other sites More sharing options...
westcoast Posted July 19, 2021 Share Posted July 19, 2021 Ironstone concretion, no fossil here but a nice piece. 1 4 Link to comment Share on other sites More sharing options...
Tidgy's Dad Posted July 19, 2021 Share Posted July 19, 2021 It's a variety of chert, sometimes known as snakeskin agate or rattlesnake chalcedony etc. 2 1 Life's Good! Tortoise Friend. Link to comment Share on other sites More sharing options...
SteveR Posted July 19, 2021 Author Share Posted July 19, 2021 Good to know - thanks! Link to comment Share on other sites More sharing options...
FranzBernhard Posted July 19, 2021 Share Posted July 19, 2021 1 hour ago, westcoast said: Ironstone concretion, no fossil here but a nice piece. 1 hour ago, Tidgy's Dad said: It's a variety of chert, sometimes known as snakeskin agate or rattlesnake chalcedony etc. 50 minutes ago, SteveR said: Good to know - thanks! (Sorry, can´t resist...) There seems to be no consensus what this is. I have no opinion . However, if it is an ironstone (siderite) concretion, this would be a new kind of weathering to me. Franz Bernhard 1 Link to comment Share on other sites More sharing options...
abyssunder Posted July 19, 2021 Share Posted July 19, 2021 I called theese "crocodile skin" concretions. 1 1 " We are not separate and independent entities, but like links in a chain, and we could not by any means be what we are without those who went before us and showed us the way. " Thomas Mann My Library Link to comment Share on other sites More sharing options...
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