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 researchers led by Princeton University scientists. The discovery provides evidence for the extraterrestrial origins of the world’s only known sample of a naturally occurring quasicrystal.
Found in a rock collected in a remote corner of far eastern Russia, the natural quasicrystal was most likely formed during the early days of the solar system, roughly 4.5 billion years ago, making the mineral perhaps older than the Earth itself, according to the research team. The results, which come three years after the team identified the mineral as the first natural quasicrystal, recently were published in the Proceedings of the National Academy of Sciences.
“The finding is important evidence that quasicrystals can form in nature under astrophysical conditions, and provides evidence that this phase of matter can remain stable over billions of years,” said physicist Paul Steinhardt, the Albert Einstein Professor in Science at Princeton and one of the leaders of the research.
Although quasicrystals are solid minerals that look quite normal on the outside, their inner structure makes them fascinating to scientists. Instead of the regularly repeating clusters of atoms seen in most crystals, quasicrystals contain a more subtle and intricate atomic arrangement involving two or more repeating clusters. As a result, 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.