I'm no expert on this but what I believe is done is you buy a special 'mesh' wire that's screwed to the studs or concrete and you use a bonding agent to adhere the marble surround to the mesh. I don't think you just bond the marble to the drywall or concrete w/o the mesh because eventually gravity would pull it away. You may already be asking this question but I just wanted to be sure.
If you have access to a quarry in your area, you can try them for the right installation materials for this job (unless you get your 'answer' here.) My best to ya and hope this helps.