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A tube of “fossilized lightning” from the Sandhills of Nebraska contains a rare type of quasicrystal that had previously only been found in meteorites and at atomic bomb test sites.
Quasicrystals are materials that break the traditional rules of crystallography. Before they were first reported in 1984, scientists believed that materials could be either crystalline – with symmetrical, repeating patterns – or amorphous – meaning randomly arranged and disordered. Moreover, scientists believed that crystals could only be symmetrical a limited number of times when rotated around an axis – two, three, four or six times.
Quasicrystals break these rules. They are assembled in an orderly pattern, but this pattern repeats itself. They also have rotational symmetries that no ordinary crystal can achieve. A quasicrystal with icosahedral symmetry, for example, can display fivefold symmetry around six different lines of rotation.
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Quasicrystals were first discovered in the laboratory. In 2012, however, Paul Steinhardt (opens in a new tab)theoretical physicist at Princeton University, and Luca Bindi (opens in a new tab)geoscientist at the University of Florence in Italy, announced the discovery (opens in a new tab) of a natural quasicrystal in a meteorite that fell on the Kamchatka Peninsula in northeastern Russia. The researchers then created more quasicrystals in the lab by mimicking the high temperatures and high pressures that might be found when rocky bodies collide. They then turned to another place where a very rapid transition to high temperature and pressure occurred: the Trinity atomic bomb test site in New Mexico. There they found more quasicrystals in the minerals below where the atomic bomb was detonated.
“Because of this, I started thinking about other materials formed under similar conditions. And I thought about fulgurites, materials formed by lightning,” Bindi told our sister site Live Science in an e-mail. -mail.
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Dramatic discharge
Fulgurites form when lightning strikes sand, fusing the grains into a gnarled, branching tube of glass. Bindi collected several fulgurites in his search for quasicrystals. The one that contained this rare form of matter came from the Sandhills of Nebraska, near the village of Hyannis. This area of ​​Nebraska is made up of grass-covered sand dunes.
The fulgurite was found near a downed power line during a storm in 2008. In total, it was about 6.6 feet (2 meters) long and up to 3.1 inches (8 centimeters) in diameter . No one witnessed the event, so researchers don’t know if lightning struck the power line and created the fulgurite, or if the line fell in the wind and created the fulgurite with its own electrical discharge.
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Either way, the resulting branched glass contained a mixture of materials from sand and metals from the power line, including manganese, silicon, chromium, aluminum, and nickel. To fuse these materials, the temperature of the sand must have briefly reached at least 3,110 degrees Fahrenheit (1,710 degrees Celsius), the researchers reported Dec. 27 in the journal Proceedings of the National Academy of Sciences. (opens in a new tab).
Quasicrystal Hunt
Using a scanning electron microscope, Bindi, Steinhardt and their colleagues found a 12-sided, 12-angled crystal with 12-fold symmetry embedded in fulgurite. Quasicrystals with this type of symmetry are even rarer than quasicrystals in general, the researchers wrote in their paper; quasicrystals with 10th order symmetry or icosahedral symmetry are more common.
The discovery points to new places to look for natural quasicrystals, Bindi said.
“This demonstrates that extreme transient pressure-temperature conditions are suitable for the synthesis of quasicrystals,” he said. Other potential places to find quasicrystals, he said, could be in impact glasses formed when large meteorites or asteroids hit Earth, or in parts of the moon’s surface. that have been hit by asteroids.
