Natural Quasicrystals

Museo di Storia Naturale, Sezione di Mineralogia, Università degli Studi di Firenze, Firenze I-50121, Italy.
Science (Impact Factor: 33.61). 07/2009; 324(5932):1306-9. DOI: 10.1126/science.1170827
Source: PubMed


Quasicrystals are solids whose atomic arrangements have symmetries that are forbidden for periodic crystals, including configurations with fivefold symmetry. All examples identified to date have been synthesized in the laboratory under controlled conditions. Here we present evidence of a naturally occurring icosahedral quasicrystal that includes six distinct fivefold symmetry axes. The mineral, an alloy of aluminum, copper, and iron, occurs as micrometer-sized grains associated with crystalline khatyrkite and cupalite in samples reported to have come from the Koryak Mountains in Russia. The results suggest that quasicrystals can form and remain stable under geologic conditions, although there remain open questions as to how this mineral formed naturally.

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Available from: Luca Bindi
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    • "Tutti i curatori partecipano a programmi di ricerca attiva sul campo e incoraggiano e includono i propri post-doc e studenti nelle attività di campo»; sul sito del Natural History Museum di Londra, in homepage e come prima notizia: «Questa estate i nostri scienziati si sono recati alle Isole Scilly per raccogliere esemplari freschi per le nostre collezioni, aiutando e sostenendo la ricerca del futuro» 12 . Dietro queste parole si vede la possibilità anche per gli " scienziati " dei musei italiani di produrre pubblicazioni accademiche ad alto fattore d'impatto, come di fatto succede (citiamo Bindi et al., 2009, come esempio a noi vicino). Tuttavia dietro la parola " ricerca " sta un insieme di attività non di prestigio accademico, che anche l'opinione pubblica tarda a configurare tra i compiti di uno " scienziato " , attività i cui prodotti sfuggono ai sistemi di rilevazione predisposti dal ministero. "

    Full-text · Chapter · Dec 2014
    • "This brings us to the question of how such a mineral can be formed in nature (Bindi et al. 2009: 1306; Bindi et al. 2011: 931). A better understanding of the formation of natural quasicrystals at different temperatures and pressures could lead to the discovery of new quasicrystals (Bindi et al. 2009: 1308). "
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    ABSTRACT: In this paper, we review the history of quasicrystals from their sensational discovery in 1982, initially “forbidden” by the rules of classical crystallography, to 2011 when Dan Shechtman was awarded the Nobel Prize in Chemistry. We then discuss the discovery of quasicrystals in philosophical terms of anomalies behavior that led to a paradigm shift as offered by philosopher and historian of science Thomas Kuhn in ‘The Structure of Scientific Revolutions’. This discovery, which found expression in the redefinition of the concept crystal from being periodically arranged to producing sharp peaks in the Bragg diffraction pattern, is analyzed according to the Kuhn Cycle. We relate the quasicrystal revolution to the non-Euclidean geometry revolution and argues that since “great minds think alike” there is a diffusion of ideas between scientific revolutions, or a resonance between different disciplines at different times. The story behind quasicrystals is an excellent example of a paradigm shift, demonstrating the nature of scientific discoveries and breakthroughs.
    No preview · Article · Mar 2014 · Philosophia
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    • "The goal was to search for naturally occurring quasicrystals—solids with quasiperiodic arrangements of atoms exhibiting Bragg peak diffraction and symmetries forbidden for periodic crystals (Levine and Steinhardt 1984; Shechtman et al. 1984). The first natural quasicrystal to have been identified, icosahedrite (Al 63 Cu 24 Fe 13 ), was recently discovered by Bindi et al. (2009, 2011) in a rock sample in the collections of the Museo di Storia Naturale of the Universit a degli Studi di Firenze (hereafter, MSNF), after a decade-long search (Lu et al. 2001). The Florence museum sample is one of two tiny (<0.5 cm) rocks known to contain the crystalline copper-aluminum alloys khatyrkite (CuAl 2 ) and cupalite (CuAl). "
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    ABSTRACT: A new meteorite find, named Khatyrka, was recovered from eastern Siberia as a result of a search for naturally occurring quasicrystals. The meteorite occurs as clastic grains within postglacial clay-rich layers along the banks of a small stream in the Koryak Mountains, Chukotka Autonomous Okrug of far eastern Russia. Some of the grains are clearly chondritic and contain Type IA porphyritic olivine chondrules enclosed in matrices that have the characteristic platy olivine texture, matrix olivine composition, and mineralogy (olivine, pentlandite, nickel-rich iron-nickel metal, nepheline, and calcic pyroxene [diopside-hedenbergite solid solution]) of oxidized-subgroup CV 3 chondrites. A few grains are fine-grained spinel-rich calcium-aluminum-rich inclusions with mineral oxygen isotopic compositions again typical of such objects in CV 3 chondrites. The chondritic and CAI grains contain small fragments of metallic copper-aluminum-iron alloys that include the quasicrystalline phase icosahedrite. One grain is an achondritic intergrowth of Cu-Al metal alloys and forsteritic olivine ± diopsidic pyroxene, both of which have meteoritic ( CV 3-like) oxygen isotopic compositions. Finally, some grains consist almost entirely of metallic alloys of aluminum + copper ± iron. The Cu-Al-Fe metal alloys and the alloy-bearing achondrite clast are interpreted to be an accretionary component of what otherwise is a fairly normal CV 3 (oxidized) chondrite. This association of CV 3 chondritic grains with metallic copper-aluminum alloys makes Khatyrka a unique meteorite, perhaps best described as a complex CV 3 (ox) breccia.
    Full-text · Article · Aug 2013 · Meteoritics & planetary science
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