I'm Stumped

[fantastic.nomadic]

I found this little guy i in Washington State, in the bed of the Carbon River, in the valley with all the stuff from Mt Rainier's last eruption. What the heck is this thing? Thanks for any help! 

 

[Ludwigia]

I'm not sure what type of rock this is, but in my opinion this is not a fossil.

[Advantage]

Also not sure what type of rock it is, but its a rock not a fossil.

[Denis Arcand]

I see a symmetry in this picture , could it be weathered mollusk shell imprint?

 

[fantastic.nomadic]

2 hours ago, Denis Arcand said:

I see a symmetry in this picture , could it be weathered mollusk shell imprint?

 

The nearly perfect bilateral symmetry was what led me to believe this was not only mineral or... Just rock. My pictures are not as adherent to the advice given so maybe I'll retake some of just this part. But... Both of those are further recessed at one end than the other and equal depth on each one. There's small details easier seen with the naked eye that very much leave the impression that they nearly identical.