How can I clean the slate?

2 questions:-
I oiled my teak outdoor furniture and some oil dripped on the slate deck and stained the slate. How can I clean the slate?

 

I want to put a new railing on my deck (slate on top of concrete). What drill bit won't damage the slate and will go through both slate and concrete?

 

Thanks,

Mike.

findstone2006-06-07 10:49:49