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Mazon nodule unknown


minnbuckeye

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Looks like a septarian concretion to me as well. My distant second guess would be pyrite. The river produces a lot of concretions with weird pyrite structures.

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I have seen coprolite with similar preservation.  Is this a river stone that was found open ??

Some of the larger coprolites I have opened have a similar structure to yours. I believe as the water in the coprolite calcified it made a pattern like this that is harder than the surrounding coprolite . Therefore, if it was an open find as it appears to be , that has rolled around in the river for a while, the softer portion disappeared and left the calcified water residual .  I'll try and post a picture of one I'm talking about.

Just my best guess. What does the outside of the concretion look like ?

Phil

Edited by flipper559
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@flipper559, @RCFossils, @connorp. I appreciate the thoughts. It did come from the river from the group hunt this summer  and was already split open. Phil, it looks very similar to yours but it also has characteristics of a septarian structure. I will keep scratching my head!!

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It most probably started out as a coprolite. Most MC concretions originally began forming around something of organic origin. Sometimes the organic matter became indistinguishable with time. Even the "duds" began their journey with something organic at their heart. I also have concretions that show this "septarian" pattern that appears as things shrink and/or dry out, similar to dried mud.

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Mark.

 

Fossil hunting is easy -- they don't run away when you shoot at them!

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After digesting the information and suggestions given above, it caused me to research how septarian nodules form. Some articles say vulcanism is required. I am assuming this is not a possibility with Mazon nodules. Other articles do not mention vulcanism. As I think about this specimen being a septarian nodule, I go back to the fact that this concretion is layered and its septarian look is only internally evident on the split section. Other septarian nodules I have found in the past are solid, not layered and the pattern extends to the surface. If someone can educate me further, I would appreciate it!!!! Is this just a septarian pattern or truly a septarian concretion. Is there a difference?

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Maybe there are polygonal synaeresis cracks? Here is a picture with incomplete polygonal synaeresis cracks:

Abb-20-Incomplete-polygonal-synaeresis-cracks-im-Sinne-Pratts-1998-Bildbreite-ca_Q640.jpg.369175bf96854ed3e163245c4bf62850.jpg

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1 hour ago, abyssunder said:

polygonal synaeresis cracks

 

 Interesting! More research to do!

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Hi,

as far as I know, vulcanism is neither necessary nor typically involved in the formation of septarian nodules.

https://en.wikipedia.org/wiki/Concretion#Septarian_concretions

Without knowing much about the Mazon creek, I am quite convinced that what you have there is a mineral infill in shrinking fissures, with the infilled mineral harder than the surrounding shrunken material, which is what a septarian nodule is made of, no matter if organic matter is involved.

Synaeresis could be called a special kind of shrinking, most typically in gel-like substrates and it is possible even under water, so plausibly here.

The overall result would look similar to mudcracks.

https://en.wikipedia.org/wiki/Syneresis_(chemistry); https://en.wikipedia.org/wiki/Mudcrack

Maybe @GeschWhat can tell more about cracks in coprolites?

Best Regards,

J

 

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On 2/5/2022 at 10:54 AM, minnbuckeye said:

If someone can educate me further, I would appreciate it!!!! Is this just a septarian pattern or truly a septarian concretion. Is there a difference?

 

Google concretion and read the Wikipedia entry. Septarian concretions are the first ones discussed. Pretty much all the info you need about concretions of all kinds is there. It's an interesting read. I like the Pillsbury Doughboy the best. :) (Although it may be the Michelin Man)

Edited by Mark Kmiecik
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Mark.

 

Fossil hunting is easy -- they don't run away when you shoot at them!

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