Decagonite

Chemical formula: Al₇₁Ni₂₄Fe₅

Decagonite is an IMA-approved mineral, a naturally occurring quasicrystal with a dominant composition of aluminum, nickel, and iron.

## Characteristics Decagonite is one of the few naturally occurring quasicrystals, making it a unique object in the world of minerals. Unlike classical crystals, whose atoms form a repeating, three-dimensional lattice, quasicrystals possess an ordered but non-periodic atomic structure. Decagonite has been found in the form of microscopic grains, usually not exceeding several tens of micrometers in size. Its observation requires advanced analytical techniques, such as scanning electron microscopy. ## Physical Properties Due to the microscopic size of the grains, determining macroscopic physical properties such as hardness, luster, or density is impossible. Analyses indicate that it is a hard and brittle material. It is opaque, and its luster is metallic. ## History and Name The name "decagonite" refers to the decagonal (ten-fold) symmetry observed in its diffraction structure, which is a characteristic feature of this class of quasicrystals. The mineral was officially approved by the International Mineralogical Association (IMA) in 2015. Its discovery is the result of research conducted by an international team of scientists, including Paul J. Steinhardt and Luca Bindi, who analyzed samples from the Khatyrka meteorite. ## Applications Decagonite has no industrial applications due to its extreme rarity and microscopic size. Its significance is purely scientific, as evidence for the existence of quasicrystals in natural, extraterrestrial conditions. It is an object of interest for specialized research institutions and museums.

Properties

Color
Gray to black
Luster
Metallic
Transparency
Opaque
Crystal system
Icosahedral

Diagnostic features

## Identification Identification of decagonite is impossible without advanced laboratory techniques. It requires the use of scanning electron microscopy (SEM) to image morphology and energy-dispersive spectroscopy (EDS) to determine chemical composition. Final confirmation is provided by electron backscatter diffraction (EBSD) or X-ray diffraction analysis, which reveals the decagonal symmetry characteristic of a quasicrystal. ## Distinguishing from similar minerals Decagonite co-occurs with other quasicrystalline phases, such as icosahedrite, and metallic minerals. Distinguishing it from icosahedrite (with icosahedral symmetry) requires diffraction analysis. It is distinguished from other metallic minerals in the meteorite by its unique chemical composition (dominance of Al-Ni-Fe) and non-periodic atomic structure.

Geological environment

## Genesis Decagonite formed under extraterrestrial conditions, within the parent planetary body (asteroid) from which the Khatyrka meteorite originated. Its formation is believed to have been the result of condensation processes in the solar nebula or shock metamorphism processes caused by asteroid collisions in space. The extreme pressures and temperatures accompanying such events enabled the formation of this unusual metallic phase. ## Mineral associations Decagonite was found in the Khatyrka meteorite, where it co-occurs with other rare minerals. Its main associate is icosahedrite (another natural quasicrystal), as well as steinhardtite, khatyrkite (CuAl₂), cupalite (CuAl), and spinel and diopside. ## Localities The only confirmed locality of decagonite on Earth is the Khatyrka meteorite. Its fragments were found during an expedition in 2011 in the Koryak Mountains in Chukotka, eastern Russia.

Rarity

Extremely rare

For collectors

## Quality criteria The quality of decagonite specimens is not assessed in the traditional way, as this mineral does not occur in macroscopic form. The scientific value of a sample depends on the size and quality of the quasicrystalline grains, their clarity in analytical studies, and their association with other rare mineral phases. Specimens are available exclusively to research institutions and major natural history museums. ## Popular localities The only known locality is the discovery site of the Khatyrka meteorite in Russia. Material from this find is extremely limited and is not available on the commercial collector's market.

Care and storage

## Cleaning Decagonite specimens occur as microscopic inclusions in the meteorite matrix and are not subject to cleaning in the traditional sense. Any operations on the material require specialized laboratory equipment. ## What to avoid Samples containing decagonite are extremely valuable from a scientific point of view. Any chemical or mechanical interference, as well as exposure to extreme temperatures that could destroy or contaminate the unique material, should be avoided. ## Storage Fragments of the Khatyrka meteorite containing decagonite are stored in specialized institutional collections, under controlled conditions (stable, low humidity and temperature), to prevent degradation of the extraterrestrial material.

External references

Sources

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