Jellybean07 Posted December 17, 2020 Share Posted December 17, 2020 More Fossils I found on my way to and from class during college in Starkville, Mississippi. This one is a material of which I found a LOT. This is maybe 50-60 mm in length? It piqued my interest there were so many sleek, shiny brown stones. There was also marcasite in this chalk bed. The Marcasite was a similar color when oxidized. Not sure if that helps with anything... This piece is actually filled with a softer material which breaks down like dried clay. I tried cleaning it out, but it was stubborn. Any ideas? 1 Link to comment Share on other sites More sharing options...
Rockwood Posted December 17, 2020 Share Posted December 17, 2020 Fragment of a cetacean mandible. Oops. Cretaceous ? Maybe not. 2 Link to comment Share on other sites More sharing options...
FranzBernhard Posted December 17, 2020 Share Posted December 17, 2020 Looks like a concretion to me. Could be the weathered (converted to limonite) marcasite that you mentioned. How do the fresh marcasite looks like (shape/outline)? It is not unusual that concretions are hollow or filled by a softer material. 10 minutes ago, Jellybean07 said: there were so many sleek, shiny brown stones. There was also marcasite in this chalk bed. The Marcasite was a similar color when oxidized. Not sure if that helps with anything... This indeed helped, providing a bigger picture. Thanks! 3 minutes ago, Rockwood said: Fragment of a cetacean mandible. Wow! That would be something! Franz Bernhard 1 Link to comment Share on other sites More sharing options...
Jellybean07 Posted December 17, 2020 Author Share Posted December 17, 2020 (edited) Thank you for your help! I only say cretaceous because the paleontological students learn it's cretaceous when they hunt for fossils right down the way from there. Much of the marcasite just kind of melts when exposed in the chalk-face. I found one bulbous marcasite piece. It was like three balls muddled together into one formation. I was wondering if they may be the limonite or concretions, but many of them are fragments, and you can tell they were hollow because they're usually round tops with equally concave bottoms, forming a little round 'cap' almost. They are most often lighter in color and slightly rougher/easier to wear down on the concave side than the convex Edited December 17, 2020 by Jellybean07 - I'm not good with geology. Limonite not concretion. Sorry! 1 Link to comment Share on other sites More sharing options...
Jellybean07 Posted December 17, 2020 Author Share Posted December 17, 2020 (edited) Though, seeing as the smaller pieces I've found are usually curved, and the "fresher" marcasite (forgive me for my lack of proper terminology) I found was like that with different caps, it could be limonite from marcasite. It makes sense for the small rounded fragments! There is also what looks like Ah-Ah Basalt right next to it (has bits of this material in tiny bubbles, I believe it's almost botryoidal if that's the term? and also black), which thoroughly confuses me. It's beautiful, you can see the almost rainbow-reflection of colors in the obsidian intermingled in the stone when it's broken. Edited December 17, 2020 by Jellybean07 Used concretion in reference to marcasite when I shouldn't have. Sorry! Link to comment Share on other sites More sharing options...
FranzBernhard Posted December 17, 2020 Share Posted December 17, 2020 Sure these look like concretions. Concretions can have very weird shapes. 12 minutes ago, Jellybean07 said: they're usually round tops with equally concave bottoms, forming a little round 'cap' almost. Are they found in-situ (still in the rock) in this way? That could mean something. Sometimes, marcasite/pyrite concretions form around organic material. I know of a local case, where the organic parts of in-situ turritellid(?) gastropods have been covered by pyrite/marcasite nodules. Can not find this paper at the moment, though. Maybe someone here on TFF is familiar with your outcrop/strata and can give more substantial information. Franz Bernhard 1 Link to comment Share on other sites More sharing options...
Mahnmut Posted December 17, 2020 Share Posted December 17, 2020 Hello, I would also tend to call them concretions, as mentioned before, they may form around fossils, but often there is not much evidence of what started them. Pyrite/Marcasite sometimes tend to decay in nasty ways, producing traces of sulfuric acid. So take care where you keep those nodules, they may damage shelves or other minerals and fossils over time. Best Regards, J 2 Try to learn something about everything and everything about something Thomas Henry Huxley Link to comment Share on other sites More sharing options...
Jellybean07 Posted December 17, 2020 Author Share Posted December 17, 2020 The hill is riding away from foot traffic and revealing all sorts of fossils, so it's more sitting atop the ground than in-situ. It's actually a heavily- landscape area, so I grabbed fossils to save them from mowers and weed-whackers. Some of the red brown concretions have an elongated shape like the first I posted, I found but circular is slightly more common, and it's usually just one small round bit away from the whole by itself. ... Oh yikes! Thank you, I'll keep these away from my fossils for sure! How interesting! Link to comment Share on other sites More sharing options...
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