Is this a fossil?

[japaris64]

Hi Everyone, I found this chunk of sandstone with some of these rusty brown spots showing.  I usually pick up chunks of shell hash on this spot along hwy 580. Some one I met there told me it was briones sandstone. I picked away at this piece and exposed more of the rusty brown  stuff but I don't know what they are.  Sort of bone shaped but ?? Any ideas? 

[Kane]

Not seeing anything distinctively fossil here, but instead nodules/concretions. Not sure where highway 580 is as I'm not in the US. Do you know the geology of the area you found it in?

[japaris64]

The online park guide - Dublin Hills Regional Park - says sandstone, shale and conglomerate. The hillside here is made entirely of this sandstone shown in this pic. 

[GeschWhat]

It could be a backfilled burrow. Can you take a closer shot of this area? 

 

Welcome to the forum!

[japaris64]

[GeschWhat]

Burrow is my guess!

[japaris64]

Thanks!

[Micah]

Iron deposits can create all kinds of weird shapes... that's what I see here, cool find!