While perusing the threads within one I came across a 'recipe' for lightweight concrete. I think they were using them for tombstones. The stones we have now are straight concrete..I'd like to give the lightweight recipe a try but I can't find it and the google search didn't give me much. I think it had vermeculite in it, a specific kind of concrete and....ugh. Blank! I'd love a good recipe if you've got one! Thanks!!