Third Natural Quasicrystal Discovered

Third Natural Quasicrystal Discovered

Author: Marek Czykanski

Normally, crystals are strictly symmetrical. However, in 1982, Daniel Shechtman, Technion – Israel Institute of technology, Haifa, discovered quasicrystals. In these types of crystals, the regular arrangement is broken up and several different basic forms alternate.

Such structures were long regarded as “impossible” in nature. However, Paul Steinhardt, Princeton University, NJ, USA, and his colleagues have already discovered two natural representatives of such quasicrystals in recent years. Both come from the Khatyrka meteorites discovered in Siberia in 2011. One of the quasicrystals resembles a ten-cornered disc stack, the other is based on icosahedral basic elements.

In the same meteorite, the scientists have discovered a third quasi-crystal. It is a mineral with the composition Al62.0(8)Cu31.2(8)Fe6.8(4). The basic geometric unit of the quasicrystal resembles an icosahedron. The composition is outside the measured equilibrium stability field at standard pressure of the Al-Cu-Fe quasicrystals reported previously. The compound is the first quasicrystal whose composition was found in nature before being synthesized in the laboratory.

The researchers suspect that the quasicrystals owe their origin to the extreme conditions they were exposed to in the meteorite. Earlier analyses have shown that the Khatyrka meteorite experienced a collision in space, and was exposed to a pressure of up to 5 GPa and heated to 1,200 °C.

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