Found this while hunting this fall.....

[SmokeHouse]

This was on a large bolder in a opening in a oak forest in Northern California. Any help on ideas are appreciated.

 

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[ANTIQUARIAN]

I'm having trouble making out exactly what I'm looking at?
It would've helped to have some depth for perspective to your pic, possibly with a coin or another object placed next to the object.

Based on the dis-colouring of the surrounding rock, I'm thinking it's possibly some type of ferrous mineral that has become trapped in the stone during the cooling process.
You might want to consider re-posting your thread here... Rocks/Gems or here... Gold Prospecting Forum

Dave

 

[Charlie P. (NY)]

I also am not sure what I am looking at. Petrified wood or something as an inclusion in the rock? Geode? Cross-section of a petrified leg bone?

 

[A2coins]

I'm thinking iron in the rock very hard to tell