How can wood, bones, and teeth from once-living organisms turn into rock? Objective Students will demonstrate the process of permineralization by using a sponge to absorb a solution of water and salt crystals. The salt crystals will fill the open spaces of the sponge & harden as the water evaporates over the course of several days. Background Permineralization is a type of fossilization that happens when minerals transported by water fill in all the open spaces of an organism or organic tissue. Within these spaces, mineral deposits form internal casts. This process occurs when water carrying m Duration: 90 Minutes.