I got a big heavy boulder of congonlerate rock (sometimes called pudding stone) from a friend.  I had it slabed and used the pieces in this one-of-a-kind coffee table.  I glued the slabs on 3/4" exterior plywood; put a thin steel band on the edge; and filled in the spaces with black grout.  I didn't have an appropriate base in my inventory at the time, so I put it on top of 4 sturdy steel 3 rod hair pin legs. I still have a piece or two of the pudding stone, but not enough to make another table like this.