11cm and 15cm hollow round rock

[Larie213]

Found 20+ intact spheres of various sizes, only broke open 2 with a 3lb sledge, the smaller one was empty, however the larger on had a 6 cm solid muddy form inside. That has since broke apart. 

[Ludwigia]

Concretions

[digit]

And very cool concretions at that. Gets me to wondering what sort of geologic processes formed hollow concretions. I understand how gas bubbles in volcanic rocks can produce voids that often fallow crystals to grow forming geodes or "thunder eggs" and how dissolution processes can erode out spaces in things like fossilized coral which can allow for beautiful botryoidal agate and druzy quartz crystals to form within. Trying to imagine the process by which these nicely concentrically layered concretions formed voids at their centers. Wish I'd taken more geology courses in college--not really required for a computer science degree.

 

No fossils of any type apparent in these but wonderful examples of geologic processes that stir the imagination and suggest a number of questions--great fun to get the gray matter activated in the morning.

 

 

Cheers.

 

-Ken

[FranzBernhard]

7 minutes ago, digit said:

that stir the imagination and suggest a number of questions

Maybe related to the formation of "Indian Paint Pots"? Maybe not?
Franz Bernhard

[digit]

Ah, spectacular! I've heard of Indian Paint Brush but have not encountered the geologic Indian Paint Pots. Something new to delve into.

 

 

Cheers.

 

-Ken

[Larie213]

Thank you for the responses, definitely an interesting topic. I did find an article about Navajo Sandstone and Moqui Marbles:

 

 

This looks very similar to the concretions I have. Interesting read, new information to expand on. I have always wanted to adventure in Utah someday. Thanks again everyone.