Everything that does not end up in sedimentary sinks is eventually recycled and lost forever to fossilization. A chemical constitute that is detached from the organism which made it. Such fossils range in composition from nearly pure carbon to complex waxes and even proteins. Impressions Formed when organic matter in a rock, such as a leaf, is removed, leaving an impression of the leaf on the rock. The original material is replaced by another mineral at a very fine scale.
Hard parts are much more commonly preserved than soft tissues.
Virtually unaltered fossils can be found in recent rocks, but are progressively more rare in older rocks. This type of preservation is unknown for dinosaurs. The process by which voids in the hard parts of organisms are filled with minerals. This is a common form of preservation for vertebrates, including most dinosaur bones, and much petrified wood where the wood cell cavities are filled with silica. The process whereby hard parts in their entirety are replaced by another material.