12/28/2023 0 Comments Petrified rockOther large pieces can also be crafted into chairs and stools. Also, larger pieces of the wood have been carved into sinks and basins. Slabs of petrified wood can be crafted into tabletops, or the slabs themselves are sometimes displayed in a decorative fashion. Not only are the fossils produced through the process of petrifaction used for paleontological study, but they have also been used as both decorative and informative pieces. Biotic remains preserved by replacement alone (as opposed to in combination with permineralization) are rarely found, but these fossils present significance to paleontology because they tend to be more detailed. The minerals commonly involved in replacement are calcite, silica, pyrite, and hematite. The slower the rate of the process, the better defined the microscopic structure will be. This can take place extremely slowly, replicating the microscopic structure of the organism. Replacement, the second process involved in petrifaction, occurs when water containing dissolved minerals dissolves the original solid material of an organism, which is then replaced by minerals. Pyritization occurs to a lesser extent in plants in clay environments. Carbonate shell material of the organism is then replaced with pyrite due to a higher concentration of pyrite and a lower concentration of carbonate in the surrounding water. This reaction between iron and sulfides forms pyrite (FeS 2). Organisms release sulfide, which reacts with dissolved iron in the surrounding water, when they decay. In marine environments, pyritization occurs when organisms are buried in sediments containing a high concentration of iron sulfides. 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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