![]() Pyritization can result in both solid fossils as well as preserved soft tissues. Pyritization is a process similar to silicification, but instead involves the deposition of iron and sulfur in the pores and cavities of an organism. Under ideal natural conditions, silicification can occur at rates approaching those seen in artificial petrification. ![]() For silicification to occur, the geothermic conditions must include a neutral to slightly acidic pH and a temperature and pressure similar to shallow-depth sedimentary environments. The specimen is transformed to stone (a process called lithification) as water is lost. In wood samples, as the process proceeds, cellulose and lignin, two components of wood, are degraded and replaced with silica. The cell walls of the specimen are progressively dissolved and silica is deposited into the empty spaces. The process begins when a specimen is permeated with an aqueous silica solution. Water must be present for silicification to occur because it reduces the amount of oxygen present and therefore reduces the deterioration of the organism by fungi, maintains organism shape, and allows for the transportation and deposition of silica. Silicification most often occurs in two environments-either the specimen is buried in sediments of deltas and floodplains or organisms are buried in volcanic ash. Studies have shown that in this process, most of the original organic matter is destroyed. A common source of silica is volcanic material. Silicification is the process in which organic matter becomes saturated with silica.
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