Is this a fossil

[No gold in NY]

Found in Arizona. At first glance I thought it was a fossilized Cypress Knee. Nah.
Someone has already sawed it off.
It is 4 inches tall and some sort of stone. Any help?

I added a third pic. Looks like the item was attached to something.
Added a closer pic of the cut end.

 

[Steve1236]

In the first pic it looks agatized around the outer ring and opalized in the center, a scratch test or short wave uv light will let you know if that's common opal, neat specimen.

 

[DDancer]

It appears to be an agate. A couple of closer pic's of the cut and polished area may help to determine if its a bit of petrified wood but I'm not seeing anything like that right now.

 

[No gold in NY]

Added a closer pic.