well if what you're saying was true then i guess we'd be seeing rocks exploding every time there was a climate change...
i'm sorry, i know this thread was made with the best of intentions but it's simply not true, and even common sense says that this is not true.
you cannot honestly believe that adding liquid to a rock makes it an unexploded bomb.
slowly heating a rock that has soaked up liquids will not make it explode.
if this were true rocks would be exploding all of the time in places such as texas, where it rains often, and then the next day temperatures raise well above 100, and in direct sunlight on black roadtops, literally hot enough to cook eggs, i've seen this i don't know how many times, and i have yet to see an exploding rock.
gradually heat them, they won't explode. if you're really paranoid, leave them out in your house for awhile and let them get to room temp, then maybe put them next to a heater or fire and let them warm up.
to be clear i am not sayign that rocks will not explode, they will, i've seen it, but only when heated rapidly. i'm not to sure about the effects that have been talked about on here that make it sound like a grenade going off, i doubt that. but i have started several campfires with old wet rocks under the ashes that have exploded, although all it added up to was a loud sound and some ash flying around, but i wouldn't say its not possible. all i'm saying is that i do not believe that SLOWLY heating the rock will cause an explosion