Silicone is soft, easily abraded, doesn't adhere well to any surface, and won't tolerate standing water so I would avoid sealants with any amount of silicone in them. I would try a urethane sealant or an acrylic adhesive type like Polyseamseal. Don't limit yourself to home hobby-craft stores like HD or even tile stores. Ask a good contractor where he buys sealant in your area. Better yet, ask the installer what he used and buy some from him if it is a custom product. If it was silicone you're probably going to be replacing it in a few years anyway so I would be careful to match the stone not just the existing sealant.

Silicone will adhere to just about anything with great force. You don't need to overthink this or overspend on the subsurface. Plain drywall was used for years with zero problems. The problems with any sheet surface for a wet area come where the seams are. And where the top caulking usually fails. There is where the corner bead of caulk needs to adhere tightly. And that's on top of the surface, in the corners, not underneath it. So, choose whatever you want for the substrate, but be sure the corners are clean, and that you use a new tube of caulk for the corner beads.

My niece gave me silicone pans for Christmas one year - we got a loaf pan, a square cake pan and a round cake pan. I made brownies in the square cake pan. I didn't like the "movement" of the pan trying to transfer a pan full of batter to the oven, as has been mentioned already. It didn't stick any more than any other pan, but I guess out of stupidity on my part, I cut up the brownies - and cut huge slices right thru the pan!!! As I said it just didn't dawn on me - who "unmolds" brownies from a pan then cuts them? You cut them in the pan! After I did it I couldn't believe I was so stupid, but it truly didn't occur to me that the knife would cut thru the pan. I have some "cutting boards" that are made out of a similar material and I obviously cut on those, so I just didn't think. So that went in the trash and I haven't used any of the others since. I think I prefer glass or metal! Altho I did switch to a silicone pastry brush and I LOVE it. And I do have some silicone spatulas as well, but I think I like the rubber ones better - the silicone is kind of stiff and that's the point of a rubber spatula - that it bends and conforms to the dish/pan. I have been thinking about buying the silicone sheets to bake on - they're awful expensive tho, so I wasn't sure they were worth the expense. Lisa

If one heats silicone to destruction, the most likely solid product will be silicon dioxide, or quartz, the primary compound in glass. It can be dissolved in hydrofluoric acid, but don't try this at home, or anywhere else. The metal it has coated may be dissolved faster and the fumes are toxic. The good news, such as it is, is that if the unbonded "glass" dust is vacuumed up or wiped up, the residue is unlikely to get in one's food, and would not be more harmful than eating outdoors in a dust storm, or eating a mud pie if one were young enough. Wiping may be better than vacuuming, depending on how well one's vacuum keeps dust out of its motor. Moving glass dust -- much like regular dust but possibly finer -- is not what you need in the vacuum's motor or in the exiting air. I would be concerned about the dust that makes it into the convection fan passages that are difficult to get to. Some consideration of the cost-effectiveness of oven replacement may be called for. In general, my condolences for the disasters that have befallen you.