I am slowly trying to get my fireplace ready for the insert which will be here Thursady. I want to put a blanket of rock or mineral wool around the firebox and on the block off plate. Only problem is I have called nearly everybody within 100 miles and nobody knows where I could get some. I remembered when I gutted one of the bedrooms a few years ago having a batt of rock wool fall out of the ceiling when I tore it down. I went up in the attic and it turns out they used a few more of them. This is from the late 1950's and it is wrapped with paper. I got a sample of it and put a propane torch flame to it. Only the tip of the flame would melt it. It did have a slight plastic burning odor so I have a feeling it has some binders in it. It did not smell or melt as badly as fiberglass does though. Am I crazy for thinking about taking that batt of wool out of the attic, removing the paper and using that to insulate the fireplace and block off plate?