They are made of Gypsum and 2 other components for strength and stability.  The original was hand carved from wood using mostly a chainsaw.  They will NOT crack, like wood, but need to be kept indoors.  They are painted with latex outdoor house paint.  If you would like to keep them on your covered porch you will need to put a coat of clear, Helmsman Spar Urethane on them.  You need to be Careful with them as they can chip if dropped.