[capt. norm]

Granite, a porous rock, is not normally affected by water infiltration as much as other rocks like limestone.

Gosh, I've had this backwards all these years, picturing limestone as porous and granite very much less so.

[Red Badger]

Well, all those black granite surface plates we use for inspection of mechanical pieces are flat to within several millionths of an inch, so I guess that’s porous.......