While I have been sitting here for the last hour reading posts, I was also boiling some granite for my tanks. Naturally I forgot the rocks. I suddenly remembered and went running in the kitchen. The pot had boiled completely dry and the burner was sitll on high. The pot was so hot I had to get oven mitts just to move it off the burner. The rocks should definitely be free of any bacteria as they have been both boiled and dry fried.