Petrified wood how would you polish?

[utahshovelhead]

I have a large piece of petrified wood collected from the Morrison formation. Its size is about 14 inches in diameter and has some crystals on the rings of the tree. I would like to polish the top only but am not sure how I would go about it as it is so rough. I have a hand held grinder with polishing pads I use on granite, but what do you recommend I do first to get the roughness to first start to smooth out?
Any response would be appreciated.

 

[old lineman]

Johnson brothers has a machine for things like that. I saw it at Quartzsite in January. Look here.


http://johnsonbrotherslapidary.com/

 

[ridgerunner]

if it is thick enough maybe you could get someone with a large saw to take a thin slice off of it.