Geologic or sea life

[Jdeutsch]

I collected this in a canyon in the Black hills of Eastern Wyoming.  I don't usually think of fossils in that region, but there happened to be a limestone column with some brachiopods about a half mile from where this rock was found, suggesting a marine environment for some of the rocks in the area.  I can't tell which geologic strata I was in, as things change quickly in the Black Hills  http://pubs.usgs.gov/sim/2777/downloads/2777_sheet1.pdf  , and there is material washing down the canyons all the time.  This was in a dry creek bed.

 

approximately 20 cm across, 10 cm wide and 10 cm thick

 

[ynot]

I see a geologic not a fossil. It could be an agate that formed around other minerals that have eroded out.

Tony

[supertramp]

something like boxwork? https://www.google.it/search?q=boxwork&biw=1280&bih=685&source=lnms&tbm=isch&sa=X&ved=0ahUKEwiPwp2nme_PAhXGuRoKHS3BB_IQ_AUICCgB

 

ciao

 

[Jdeutsch]

Boxwork is very reasonable, as I've found and collected it in the same canyon where cliffs collapse and expose pockets.  See image.

 

The boxwork collected was much more fragile than the specimen which started the thread, but is certainly has similarities