An Extra-Terrestrial Quasi-Crystal

Researchers report that a rock fragment containing a previously undescribed natural quasi-crystal might be a remnant of a 4.5 billion-year-old meteorite. Unlike crystalline solids, quasi-crystals contain a quasi-periodic arrangement of atoms and symmetries not normally found in crystals. 

A rock sample containing quasicrystals unearthed in the Koryak Mountains in Russia.

Credit: Paul Steinhardt, Princeton University

Paul J. Steinhardt and colleagues performed mass spectrometry and oxygen isotope analysis on quasi-crystalline grains of iron, aluminum, and copper arranged in a pattern with icosahedral symmetry (six separate axes of five-fold symmetry)and embedded in a fragment of rock previously unearthed in the Koryak Mountains of Russia. 

The quasi-crystals, the authors report, were intermeshed with silicates and crystalline metals. In addition, the rock fragment contained a quasi-crystalline grain encased in stishovite, a mineral with the chemical composition of silica that forms only under extremely high pressures typical of the Earth's deep mantle and of meteoritic impacts. 

According to the authors' dating analysis, the fragment's oxygen isotope signature, which resembles that of certain carbonaceous meteorites, suggests an extra-terrestrial origin, possibly a meteorite that originated in the early solar system around 4.5 billion years ago. The events that led to the extraordinary assemblage of minerals found in the rock fragment remain a mystery, but the findings suggest that quasi-crystals--until recently represented exclusively by man-made materials--can form in nature and remain stable over cosmic time scales, according to the authors.

Contacts and sources:
PNAS News Office 
Proceedings of the National Academy of Sciences

Article #11-11115: "Evidence for the extra-terrestrial origin of a natural quasicrystal," by Luca Bindi et al.

 Paul J. Steinhardt, Princeton Center for Theoretical Science, Princeton University, Princeton, NJ