Permineralization, a type of fossilization, involves deposits of minerals within the cells of organisms. Water from the ground, lakes, or oceans seeps into the pores of organic tissue and forms a crystal cast with deposited minerals. Crystals begin to form in the porous cell walls. This process continues on the inner surface of the walls until the central cavity of the cell, the
lumen, is completely filled. The cell walls themselves remain intact surrounding the crystals.
Silicification In
silicification, the
weathering of rocks releases
silicate minerals and the
silica makes its way into a body of still water. Eventually, the mineral-laden water permeates the pores and cells of some dead organism, where it becomes a
gel. Over time, the gel will
dehydrate, forming an
opaline crystal structure that is an internal cast of the organism. This accounts for the detail found in permineralization. Silicification reveals information about what type of environment the organism was likely to have lived in. Most
fossils that have been silicified are
bacteria,
algae,
Carbonate mineralization Carbonate mineralization involves the formation of coal balls.
Coal balls are the fossilizations of many different plants and their tissues. They often occur in the presence of seawater or acidic peat. Coal balls are calcareous permineralizations of peat by
calcium and
magnesium carbonates. Often spherical in shape and ranging from a few grams to several hundred kilograms in mass, coal balls are formed when water containing carbonate permeates the cells of an organism. This type of fossilization yields information about plant life in the Upper
Carboniferous Period (325 to 280 million years ago). '' in Holzmaden Shale
Pyritization This method involves the elements
sulfur and
iron. Organisms may become pyritized when they are in marine sediments saturated with iron sulfides. (
Pyrite is iron sulfide.) As organic matter decays it releases sulfide which reacts with dissolved iron in the surrounding waters. Pyrite replaces carbonate shell material due to an undersaturation of carbonate in the surrounding waters. Some plants become pyritized when they are in a clay terrain, but to a lesser extent than in a marine environment. Some pyritized fossils include
Precambrian microfossils, marine
arthropods and plants. ==Scientific implications==