metamictic

Metamictic refers to a phenomenon observed in certain minerals where their crystalline structure has been destroyed due to radioactive decay. This decay, primarily from alpha particle bombardment, causes internal damage within the mineral's lattice. Over geological timescales, the cumulative effect of this damage can lead to a complete loss of crystallinity, rendering the mineral amorphous.

Minerals that are prone to metamictization are typically those containing radioactive elements like uranium and thorium, such as zircon, monazite, and pyrochlore. The process of metamictization is often accompanied by changes in the mineral's physical properties. For instance, metamict minerals may become isotropic, meaning they exhibit the same physical properties in all directions, unlike their crystalline counterparts which are anisotropic. Their hardness can decrease, and they may become more susceptible to weathering.

The degree of metamictization can vary, ranging from slight internal disorder to complete amorphization. The process is influenced by factors like temperature, pressure, and the concentration of radioactive elements. Despite the loss of crystallinity, metamict minerals still retain their original chemical composition. Metamictization is a significant consideration in geology and materials science, particularly in fields like geochronology, where the dating of minerals is crucial, and in the study of radioactive waste containment materials.