Natural quasicrystal with decagonal symmetry

Area of Science:

• Materials Science
• Cosmochemistry
• Mineralogy

Background:

• The Khatyrka meteorite, a CV3 carbonaceous chondrite, has previously yielded the first natural quasicrystal, icosahedrite.
• Natural quasicrystals are rare and provide unique insights into material formation under extreme conditions.

Purpose of the Study:

• To report the discovery and characterization of a new natural quasicrystal with decagonal symmetry.
• To investigate the formation conditions of quasicrystals in meteorites and their implications for early solar system processes.

Main Methods:

• Discovery and identification of the quasicrystal within the Khatyrka meteorite.
• Compositional analysis of the quasicrystal (Al71Ni24Fe5) and associated minerals.
• Laboratory studies on the stability of synthetic decagonal Al71Ni24Fe5.

Main Results:

• The first natural quasicrystal with decagonal symmetry, Al71Ni24Fe5, was identified in the Khatyrka meteorite.
• This quasicrystal was found alongside other minerals, including icosahedrite, steinhardtite, trevorite, and taenite.
• Laboratory data indicate that decagonal Al71Ni24Fe5 is stable between 1120 K and 1200 K, supporting prior conclusions about the meteorite's thermal history.

Conclusions:

• The discovery of natural decagonal quasicrystals in meteorites provides evidence for high-temperature events and rapid cooling in the early solar nebula.
• The presence of metallic aluminum alloys (Al-Ni-Fe, Al-Cu-Fe) in meteorites raises new questions about the chemical and physical conditions in the early solar nebula.