In geology, petrifaction, petrification or silicification's the process by which organic material's converted into stone by impregnation with silica. It's a rare form of fossilization. Petrified wood's the most well known result of this process, but all organisms from bacteria to vertebrates can be petrified. Process A major ingredient in the cell walls of wood's cellulose. Under certain conditions, the silica binds to the cellulose; when it crystallizes, it preserves the microscopic structure… (More on Petrifaction)