The science fiction writer Isaac Asimov declared:  “Stone, my friends, was humanity’s first non-renewable resource.  Luckily there is so much of it that it never became scarce!”  In a seminar on the future of space as a non-renewable resource, it was clear where Asimov was going:  he was going to cover Alpha to Omega, everything from the origin of stone technology to the positioning of satellites in orbit, and further concerns beyond the earth’s gravitational pull.  But he didn’t spend long on stone, the resource that didn’t become scarce.