Model of a quasicrystal. (Image courtesy of Paul Steinhardt)
A rare and exotic mineral so unusual that it was thought impossible to exist came to Earth on a meteorite, according to an international team of scientists led by Princeton physics professor Paul Steinhardt. The mineral, called a quasicrystal, has an intricate internal structure quite different from conventional crystals, resulting in different physical properties, such as being harder than crystals made of similar elements.
Although quasicrystals can be made in a laboratory, they were not thought to exist in nature until Steinhardt, the Albert Einstein Professor in Science, with Princeton senior research scholar Nan Yao and Luca Bindi of the Florence Natural History Museum in Italy, identified the first known natural quasicrystal in a sample from a storage box at the Italian museum. They published the finding in the journal Science in 2009. Steinhardt and Bindi then traced the origin of the sample to a remote corner of far eastern Russia where mineralogist Valery Kryachko had collected it in 1979.
After arranging a collaborative agreement between Princeton and scientists at the Russian Academy of Sciences’ Institute of Ore Mineralogy, a team including Steinhardt, Bindi, Kryachko and scientists from Cornell University and the Smithsonian Institution made an expedition to the Koryak Mountains in Russia’s Kamchatka Peninsula to search for more quasicrystals. During 2011, they also examined the original sample with the help of Princeton Professor of Geosciences Emeritus, Lincoln Hollister, as well as with collaborators at the California Institute of Technology and the Smithsonian Institution. The researchers concluded that the quasicrystal was originally from a meteorite, which they reported in January 2012 in the journal Proceedings of the National Academy of Sciences.
In August 2012, Steinhardt and Bindi reported in the journal Reports on Progress in Physics that the Russia trip yielded new samples that have allowed the scientists to verify the crystals’ meteoritic origin. The expedition also showed that the quasicrystals arrived on Earth roughly 15,000 years ago during or after the last ice age, and most likely formed during the early days of the solar system, roughly 4.5 billion years ago, making them perhaps as old as the Earth itself.
A vehicle fords a river in the northeastern part of Russia’s Kamchatka Peninsula during an expedition by a team of Princeton researchers and colleagues to the Koryak Mountains to search for quasicrystals. (Image courtesy of Paul Steinhardt)
“The finding of these new samples confirms that quasicrystals can form in nature under astrophysical conditions,” Steinhardt said.
Although quasicrystals are solid minerals that look quite normal on the outside, their inner structure makes them fascinating to scientists. A quasicrystal’s atoms can be arranged in ways that are not commonly found in crystals, such as the shape of a 20-sided icosahedron with the symmetry of a soccer ball. The concept of quasicrystals — along with the term — was first introduced in 1984 by Steinhardt and Dov Levine, both then at the University of Pennsylvania. The first synthetic quasicrystal, a combination of aluminum and manganese, was reported in 1984 by Israeli materials scientist Dan Shechtman and colleagues at the U.S. National Institute of Standards and Technology, a finding for which Shechtman won the 2011 Nobel Prize.
The samples they found have been accepted by the Meteoritical Society as evidence of a new meteorite called Khatyrka. The research was supported by NASA and the National Science Foundation’s Materials Research Science and Engineering Centers through a grant to the Princeton Center for Complex Materials and New York University.
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