Vnaz50 Posted March 2, 2021 Share Posted March 2, 2021 Is it typical to have such clean circular breaks in different areas of chert? Pictures 2&5 Link to comment Share on other sites More sharing options...
ynot Posted March 13, 2021 Share Posted March 13, 2021 Looks more like sandstone. Darwin said: " Man sprang from monkeys." Will Rogers said: " Some of them didn't spring far enough." My Fossil collection - My Mineral collection My favorite thread on TFF. Link to comment Share on other sites More sharing options...
Blastoid Posted March 15, 2021 Share Posted March 15, 2021 Not sure what you’re referring to, but I’d suggest two possibilities: fossil remnants, like small brachiopods, or areas where a softer material was eroded away. Much Ontario chert is found as layers of nodules in soft sedimentary limestone or dolostone. It can have odd looking indentations, when the once-enclosing, much softer limestone is weathered away. I am fond of Ontario chert. Attached is a photo of a pretty one from the shores of Lake Huron, collected last week. Link to comment Share on other sites More sharing options...
Vnaz50 Posted March 16, 2021 Author Share Posted March 16, 2021 In the first picture there is a place at the top in the middle and at the bottom right corner. On the last picture it’s also at the bottom right. They look like very smooth circular breaks Link to comment Share on other sites More sharing options...
Vnaz50 Posted March 18, 2021 Author Share Posted March 18, 2021 Here is another with the circular break on it. Link to comment Share on other sites More sharing options...
digit Posted March 18, 2021 Share Posted March 18, 2021 Don't know if I'd call the circular area a break-looks more like an erosional feature. Still no fossils in this piece--just a black rock with some marginally interesting shaping. Cheers. -Ken Link to comment Share on other sites More sharing options...
Vnaz50 Posted March 21, 2021 Author Share Posted March 21, 2021 And I’m assuming this just eroded in a circle also? Link to comment Share on other sites More sharing options...
digit Posted March 21, 2021 Share Posted March 21, 2021 Quite likely. Circles and, in general, roundish forms are usually the result of erosional forces gradually knocking/wearing off the high points (sharp corners and edges) till rocks form rounded cobbles. This is commonly seen in river rocks and is the same principle used in rock tumblers to convert angular starting material into smoothly rounded polished stones. I see no details in the structure to suggest this rounded rock is in any way a fossil. The texture seems to indicate some sort of sedimentary rock. Hard to see without a side view but it appears this has a flattened side. This could be from a more rounded cobble that broke through on a weaker bedding plane that sliced the rounded shape in two. That's my guess without having this rock in hand to inspect closer. Cheers. -Ken Link to comment Share on other sites More sharing options...
Vnaz50 Posted March 21, 2021 Author Share Posted March 21, 2021 Thank you very much for that explanation Link to comment Share on other sites More sharing options...
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