• DOI:10.1126/science.1170827
• Corpus ID: 14512017

Natural Quasicrystals

@article{Bindi2009NaturalQ,
  title={Natural Quasicrystals},
  author={Luca Bindi and Paul J. Steinhardt and Nan Yao and Peter J. Lu},
  journal={Science},
  year={2009},
  volume={324},
  pages={1306 - 1309}
}

• L. Bindi, P. Steinhardt, +1 author P. J. Lu
• Published 5 June 2009
• Geology
• Science

Forbidden Crystals In crystalline materials, a unit cell is replicated in space through a series of rotations, inversions, and reflections. In order to fully fill space, only certain rotational symmetries are allowed. Quasicrystals contain aperiodic tilings of two or more basic shapes that allow these forbidden rotation symmetries. A number of quasicrystalline materials have been synthesized in the lab, including a number of aluminum alloys. Bindi et al. (p. 1306) examined samples of the mineral khatyrkite, with a nominal composition of (Cu,Zn)Al2. A number of quasicrystalline grains with composition similar to synthetically formed materials were observed. Thus, quasicrystals can form in nature under geological conditions. A sample of the mineral khatyrkite contains quasicrystals, which are ordered but lack the translational symmetry of crystals. 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.