Found in river in Mcloud California. Posted in a what is this thing group.

[BrittaneyM]

[Kane]

I would say a concretion.

[BrittaneyM]

That is what I’m finding as well. It has such a unique look to it 

[DPS Ammonite]

Looks like spheroidal weathering in an igneous rock such as basalt. Better up close pictures I think will show pheonocrysts.

 

https://epod.usra.edu/blog/2015/06/spheroidal-weathering-in-a-basalt-outcrop.html

Edited July 26 by DPS Ammonite

[automech]

Welcome to the Forum from Maryland. That's a real cool looking rock! I'd put it on my fireplace mantle.

[Mark Kmiecik]

Great example of a concretion. Nice find!