Fossilization is he act and result of fossilizing: transform into fossil. Fossil is called, in as much, to the element of organic origin that, with the passage of time, is petrified (that is, he turned to stone).

Sediment intervention

When dying a organism, the decomposition of its remains begins. Due to various factors, such as the intervention of animals and bacteria or the action of water, these remains are disintegrated; however, this process is not carried out if the corpse is quickly covered by sediment.

Ammonite fossilization

Ammonite fossilization is possible thanks to silicification

Underground, the participation of mechanical and biological agents is reduced. This is how fossilization can occur, especially of hard parts (such as bones), since the soft parts (the viscera, the muscles, etc.) continue to be exposed to microorganisms.

Fossilization begins, in this way, when the soft parts disappear and the remaining spaces are filled by sediments. From then on, various chemical transformations that lead to the substitution of organic elements by minerals.

If it is the remains of an animal, then the soft organic matter becomes a very rich mass of nutrients, which the bacteria consume. In a case like this, it is common for oil to form. On the other hand, the remains of plant origin give rise to humus, which sometimes turns into charcoal.

Total mineralization of the remains

If the conditions are right, a total change of the molecules takes place in a very long period of time. Fossilization is complete when the remains of the organism are completely mineralized, becoming stone.

Fossils, if well preserved, offer important information about life in times past. The paleontology It is the science that is dedicated to analyzing the fossil remains to know the characteristics of the living beings that inhabited our planet long ago.

It is important to bear in mind that, beyond the success of fossilization, if a fossil reaches the surface, it is most likely that it will begin to suffer the effects of fossilization. erosion and get damaged. It can even degrade completely.


This is the name for the most common fossilization process. The hard parts of the remains are replaced by calcium carbonate in the form of calcite, the most abundant mineral in sedimentary rocks. As an interesting fact, this mineral is also present in the shells and shells of a large number of invertebrates, which increases the presence of this process in nature.

The skeleton of corals is also made up of calcite, something that accelerates fossilization and allows its details to be preserved in an exceptional way. Aragonite is another form in which calcium carbonate can be found in the shells of various mollusks, although it becomes calcite since its structure provides greater stability.


In some cases, the role of the fossilizing agent is assumed by certain chemical solutions arising from silica, particularly in the form of chalcedony, the most stable and frequent. Siliceous fossils can also be found in limestone rocks, something common in echinids, foraminifera, gastropods, brachiopods and ammonites.


If there is no oxygen in the environment, it generates hydrogen sulfide. Its reaction with the salts of the Water of the sea gives rise to iron sulfides (especially pyrite and marcasite), which replace the organic matter in skeletons and shells. The fossilization that goes through this process is characterized by metallic-looking bodies.

Forest fossilization

Carbonification begins with the accumulation of leaves and trunks without oxygen


In the case of arthropod remains whose skeleton is composed of chitin or plants with cellulose, carbonification is the most frequent fossilization process. When leaves and trunks accumulate in an environment without oxygen, humus appears first, and then carbon, until reaching the Coal.

Almost all the coal mines arose during the terrestrial period known by the name of carboniferous, when the planet was full of dense forests. This fossilization process spread over more than 60 million years.