as a result of meteorite impacts producing an extreme pressure and high temperature environment. Radioactive decay A common example of a radioactive decay alteration is when a radioactive element bearing zircon or allanite crystal becomes metamict or amorphous due to structural damage. Serpentinization Serpentinization is the mineral alteration process that results in the formation of serpentine group of minerals mainly from the olivine group, with hydration and changes in pressure as major factors. Dolomitization Dolomitization refers to the varied suggested manners in which a predominantly calcite rich calcium bearing sedimentary rock such as limestone may alter into the magnesian dolomite rich rock dolomite. Diagenesis is a likely culprit that involves volumes of water and fairly low heat, as an ionic exchange catalyst. The reaction is as follows: 2CaCO3(limestone) + Mg2+ -> CaMg(CO3)2(dolomite) + Ca2+ Pyritization Pyritization involves the ionic replacement by iron and sulfur atoms that combine to form the mineral pyrite. Opalization Opalization is the alteration of amorphous silica, often as organic remains of siliceous microfossils in lithified sedimentary rocks, into the mineraloid opal. Uralitization Uralitization is the process of deuteric alteration of pyroxene (most commonly augite) to form amphibole (actinolite-tremolite). The alteration occurs during either late-stages of magmatic crystallization at low temperatures (< 500 °C) or during low-grade metamorphic events (sub-greenschist facies metamorphism). The reaction is paramorphic, meaning that the structure of the mineral is modified, but its original chemistry is retained. References Mineralogy