Icosahedrite

• IMA 2010-042

Icosahedrit is an extremely rare mineral from the class of mineral elements, more specifically the metals, intermetallic compounds and alloys. The mineral has the empirical composition Al63Cu24Fe13. Icosahedrit is so far the only known mineral in the form of quasicrystals. So far, only one sample of this mineral was found in a Siberian meteorite.

Special Features

Since it is an extremely rare mineral is the Icosahedrit and the quasicrystals found so far had edge lengths of up to 1 to 2 mm, were many variables such as stroke, hardness, etc. not yet determined.

Etymology and history

The name Icosahedrit refers to the macroscopic expression of quasicrystals. These formed from among the specimens found icosahedron. The mineral was first described by Luca Bindi and Paul J. Steinhardt on samples of a meteorite, which was found in 1979 on the Siberian Chukchi Peninsula. This prompted the first to describe in 2010 on an expedition to Siberia, in the course of a meteorite was found, which is regarded as type material for Icosahedrit today. In the same year the mineral by the IMA was officially recognized.

Classification

In Icosahedrit is one among the metals to be counted intermetallic compound or alloy. A classification according to Strunz bzw.Dana there has not, as these classifications to build exclusively on crystals, but not on quasicrystals (as of 2012). The classification by Hölzel was extended to quasicrystals. Here the Icosahedrit under number 1.AK.100 (metals, intermetallic compounds and alloys; subgroup quasicrystals ) out.

Education and Locations

The single known locality is a meteorite that fell in Korjakengebirge on the Siberian Chukchi Peninsula. Based on the locality is believed that the meteorite 15,000 years ago struck there, as the remains were found in glacial sediments. The type material is located in the Museo di Storia Naturale of the University of Florence (catalog 46407 / G). It is not known whether there may be Icosahedrit purely terrestrial origin.

Crystal structure

Icosahedrit does not form crystals with translational symmetry, but rather quasi-crystals. X-ray diffraction analyzes show the typical for quasicrystals fivefold symmetry. In the samples known to date, it was not according to the analyzes to ( quasi ) single crystals but aggregates.

The classification is A6d = 12.64 Å in the usual quasi- crystalline 6-dimensional notation. Since there are no elementary cells in quasicrystals, only an empirical chemical composition can be specified.