I did a little googling and several sources confirm that the stone has been cleaned, so no chance of examining a patina. It's so heavy it can't be moved to a museum.
“Interesting” is one way to put it. :’)
Before I posted the topic, I’d gotten a FReepmail from one of the pro-Mormon zealots from my anti-Christian cadre dedicated to the election of Mitt Romney and revival of The Dry Look from Gillette (that’s a series of jokes in there, everyone, so don’t write in, okay? But it’s a fact that the wet head is dead, learn to live with it) with some photo links to the stone, one of which lead to this thorough discussion of it:
The Los Lunas Decalogue Stone
Maintained and written by J. Huston McCulloch
http://www.econ.ohio-state.edu/jhm/arch/loslunas.html