...cuz I heard that certain rocks explode. --but marble is metamorphic, which is stable.i have 2 pieces of marble I'd love to incorporate into my coming cob oven. I also plan to use fire bricks. Thoughts?
I am using soapstone--got some scraps from the Habitat Re-Store for a song, cheaper than firebrick.
I think marble will crack along the grain lines. But if it is bedded well, it will be a stable crack in the floor but still usable.
"You must be the change you want to see in the world." "First they ignore you, then they laugh at you, then they fight you, then you win." --Mahatma Gandhi
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I don't know about granite, but I have always heard not to use river/creek rocks for fireplaces. Through the years, river rocks can absorb a fair quantity of water. If they are then placed next to a heat source, that trapped water can quickly expand, often enough to explode.