Permineralization fossils are the most typical process for fossilization. A bone, piece of wood, or shell buried in sediment may be exposed to water rich in minerals after the water has passed through the residue. This water will fill in the gaps with minerals, usually silica, and create a fossil.
When minerals carried by water fill in all the gaps in an organism or organic tissue, this process is known as permineralization, a sort of fossilization. Mineral deposits create internal castings within these cavities.