Another from Mazon Creek

[KimS]

Any ideas on this one?
It was found near Braidwood, IL while hunting for concretions.
It seems like a mold or a cast of something.
It's about the diameter of a pen, and has a definite spiral shape.
Thanks for you help!
Kim

 

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[bakergeol]

Well it probably is a cast from a gastopod(snail). I would have considered it a coprolite but the spirals are too perfect.
.

George

 

[KimS]

George,
Hi!
I think you're right on!
I got some help from Russ Jacobsen at the isgs (see the other mazon creek posting). He sent the pictures on to a friend who feels it is pyrite.
"The spiral specimen, if it is from a strip mine, is pyrite. I have seen these pyrite structures in Pit 11 or it might be one of those a spiral concretion (unlikely a coprolite, despite its shape)."

I've looked up pyritized shells in shale on line, and it seems to fit.
Thanks!
Kim

 

[bomber]

been there a couple of times,cool place