Metamictization

Metamict (formerly also pyrognomisch ) is the name of a crystal, the crystal structure was destroyed by nuclear radiation.

In crystals having a relatively high content of radioactive elements, the atoms are ejected from their lattice sites because of the radioactive radiation, and not return to its original position. This is the previously crystalline state to an amorphous quasi- glass-like state. In compounds with little salt distinctive character of the negative effect on the crystal lattice is particularly high.

The material usually retains its outer, crystalline appearance, density and transparency decrease, however, and the color changes from green or brown to opaque black. In addition, the gloss decreases and is pechartig. The cleavage is lost, but it shows a striking muscheliger break.

Metamikte crystals are referred to as isotropierte or isotropisierte crystals since their original direction-dependent ( anisotropic ) properties such as hardness and refractive index are now independent of direction.

The Isotropierung can often be "repaired" by heating. The heat, the atoms return back to her place, where energy is also free, which can be expressed by a visual glow (see thermoluminescence ). The so-called Wigner energy is based on the Isotropierung of graphite moderators.

Examples of metamikte crystal finds for minerals include allanite, Blomstrandin, Betafit, columbite, euxenite, fergusonite, gadolinite Samarskite, thorite and zircon. Other minerals such as uraninite, thorianite and Yttrotitanit despite their high levels of uranium and thorium often have little isotropisiert. It is believed, therefore, that their crystal lattice have good regeneration properties.