I'm designing a mahagony coffee table and would like to have a wooden
frame with a stone insert -- preferably a green granite or marble --
for the table surface. This raises a few questions that
possibly someone could help me with:

1) How thick should I make the granite/marble? The table top is 32"
by 54", so I am planning to make a rabbetted frame with 4" wide rails
and stiles using 1" thick mahagony. That leaves about 24"x46" for the
stone. In addition to the rabbets, I am planning on using three
1x1's running across the underside of the frame to further support the
stone. I'm guessing that the weight of the stone shouldn't be an
issue, but maybe I'm wrong.

2) Any suggestions about where one can get a nice piece of 22"x44"
granite of the right thickness for furniture? Chicago area? A friend
already cautioned me to cut out an MDF template to give to the stone
dealer to be sure that the size is perfect. Any other advice?

Thanks.