![]() Trees, however, are not the only petrified life. Many of these fossils retain so much of the appearance of the trees that the original species and growth habits can be identified. The best known petrified fossils may be petrified forests. Iron-rich solutions require sulfur to form fossils, so iron-petrified fossils most commonly occur in marine environments, with some rarer examples found in clay. Carbonate solutions can develop in marine and non-marine environments, but they most commonly occur in marine environments because calcium carbonate forms more easily in marine environments. Silica-enriched water develops in areas with igneous rocks like granites, basalts and especially volcanic ash. The crystals from iron solutions tend to grow larger, showing the major structures of the organism but not the finer details.Įnvironmental conditions determine the type of mineral that petrifies fossils. Carbonate solutions also deposit as very fine-grained crystals that mimic the original cell structures of the organism. The microscopic quartz crystals replace the cell material bit by bit, often creating a duplicate in stone of the original organism, even in some cases down to detailed replication of the internal structure of cells. When silica solutions fill in the cell structure, extremely fine-grained cryptocrystalline quartz forms. The type of material deposited determines the level of detail in the resulting fossil. Most petrified fossils form from silicates, carbonates or iron. Shells, bones and plants, especially trees, are particularly suited to permineralization because the natural structures of the cells maintain their shape during burial and the replacement process. Eventually the deposited minerals replace all of the organic material. ![]() As the cells slowly decay, the solution fills in the gaps left behind. The dissolved minerals in the solution crystallize between the cells of the organism. As the water evaporates, the minerals remain. Over time, these mineral-rich solutions seep into and saturate the buried remains. Water containing dissolved minerals circulates through the sediments. Burial slows the decomposition rate enough to allow the replacement to happen. Petrifying begins with the quick burial of plant or animal material. Over time, minerals entirely replace the organic material, creating a petrified fossil. Solutions containing silicates, carbonates, iron or other minerals seep into the gaps and spaces between the cells, first encasing the cells and eventually replacing the cells themselves. Petrified fossils result from permineralization, the replacement of once-living matter by minerals.
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