Using Dad's rocks was the natural thing to do, but it turned out on close inspection that there weren't stones large enough and solid enough, without veins or fissures that would split under stress, for the two base stones and the top slab, so I figured I would have to acquire granite for them. I visited several places that advertise marble and granite; most dealt only in 1 inch sheets for countertops. At a monument manufacturing facility on Oracle I was told that I can place an order for a stone to be shipped in several months from the northeastern US, or I could go to a quarry. Where is a quarry? In the northeast. It was funny to hear this in the shadows of the Santa Catalinas, but that's how it is.