Collisions in outer space produced an icosahedral phase in the Khatyrka meteorite never observed previously in the laboratory

Author(s): Bindi, Luca; Lin, Chaney; Ma, Chi; Steinhardt, Paul J.

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 Abstract: We report the first occurrence of an icosahedral quasicrystal with composition Al-62.0(8) Cu-31.2(8) Fe-6.8(4), outside the measured equilibrium stability field at standard pressure of the previously reported Al-Cu-Fe quasicrystal (AlxCuyFez, with x between 61 and 64, y between 24 and 26, z between 12 and 13%). The new icosahedral mineral formed naturally and was discovered in the Khatyrka meteorite, a recently described CV3 carbonaceous chondrite that experienced shock metamorphism, local melting (with conditions exceeding 5 GPa and 1,200 degrees C in some locations), and rapid cooling, all of which likely resulted from impact-induced shock in space. This is the first example of a quasicrystal composition discovered in nature prior to being synthesized in the laboratory. The new composition was found in a grain that has a separate metal assemblage containing icosahedrite (Al63Cu24Fe13), currently the only other known naturally occurring mineral with icosahedral symmetry (though the latter composition had already been observed in the laboratory prior to its discovery in nature). The chemistry of both the icosahedral phases was characterized by electron microprobe, and the rotational symmetry was confirmed by means of electron backscatter diffraction. Electronic Publication Date: 8-Dec-2016 Citation: Bindi, Luca, Lin, Chaney, Ma, Chi, Steinhardt, Paul J. (2016). Collisions in outer space produced an icosahedral phase in the Khatyrka meteorite never observed previously in the laboratory. Scientific Reports, 6, doi:10.1038/srep38117 DOI: doi:10.1038/srep38117 ISSN: 2045-2322 Type of Material: Journal Article Journal/Proceeding Title: Scientific Reports Version: Final published version. This is an open access article.