When you look at a granite headstone in a cemetery, you think it'll last forever. Especially if it's a brand new gravestone with a high polish to it. But keep walking, especially through the older sections of a cemetery, and you will see just how much damage the weather and seasonal changes can inflict on a granite grave marker. Sometimes if enough water is absorbed into the stone and it freezes, whole sections of granite can crack and split away from the main stone. The good news is that products are available to put granite gravestones back together again.
Lay a tarp on the ground, and try to assemble the broken pieces on it. Determine if you must glue the pieces back together or glue them together and surface fill them once they're reattached to the main part of the headstone.
Wash the edges of the mating edges of the broken granite pieces with a non-ionic cleaner purchased from a janitorial supply store. These cleaners don't leave salts behind on the surface of the stone. Dip a soft-bristle brush in the cleaner, scrub the granite clean and rinse with clean water.
Make sure the granite is dry before mixing the granite epoxy per the manufacturer's directions to glue the pieces back together. Make sure the epoxy is rated for outdoor use and is epoxy-based as opposed to a polyester-/resin-based glue.
Spread the epoxy on the mating surfaces of two granite pieces with a putty knife, and press the sections together. Wipe away any epoxy from the surface of the stone. To keep pressure on the two granite sections while the epoxy is setting up, wrap duct tape around them. Continue gluing pieces together and binding them with duct tape.
Remove the duct tape of the individually glued sections after 24 hours before starting to glue the larger sections back on the main headstone. Apply duct tape to exert additional pressure.
Remove the duct tape 24 hours later. If there is any surface filling required, use a marble and granite surface repair kit. The kit provides different colours of granite dusts. Mix the dust with a two-part adhesive per manufacturer's directions. After mixing, use a putty knife to fill any indentations on the surface of the gravestone.
Shave any excess filler from the surface of the stone once the mixture starts to harden. Finish by polishing the filler using a series of abrasive grit pads and polishing compound, moving from medium grit to very fine.