Steve B wrote:
"Bob F" wrote

If the fireplace is ever going to be used without the insert, I'd
probably use firebrick on the inside of the fireplace. The granite
would probably crack quickly.


A friend of mine owns a granite company. A friend of his did a free
video for him, as he was learning his videography skills. The video
shows the advantages of granite. In one sequence, they take a large
propane weed burner and turn it on the underside of the granite. On
top, there is a pan of water. They get the water to boil vigorously.
I know granite is good stuff. I have owned a lot. But, I don't know
what the cracking limits on it are, I think it may vary heavily with
the graining and natural cracks already there. Still, installed
flat, and properly supported, I would think it would be pretty
durable. Just buy pieces with no obvious cracks. Maybe even the
1.25" thick instead of the .75", too. Some smaller chunks might be a
lot cheaper, too.

The problems I would think relates to constant variations in heat to different
parts of the slab. Expansion/contraction is going to take its toll. Even
firebrick gives out eventually in many cases.