Another geological posing as biological?

[daves64]

First off, not all the pics do this much justice. Brand new camera & not quite sure on lighting yet. Anyhow, I found this the other night while outside at work. I looked down at the river rock landscaping in this one area & saw what looked like a shadow that was at the wrong angle with the light, so I picked it up. Took it inside & this is what I had found. 4.5 cm long x 4 cm wide x about 1.75 cm thick weighing 27.2 gm. Some of the edge views show what looks like more extending down into whatever the matrix is. It doesn't fizz with hydrogen peroxide. I keep thinking shell when looking at it, but I could be mistaken. Found in Central Washington State from rock dredged from the Yakima River.

[Fossildude19]

Yes. No fossil, unfortunately.  

Keep looking, though. 

Regards,