Jan. 9, 2012

The mystery of how a highly unusual material found in a rock from a Russian mountain could have been created naturally on Earth may have been answered: It didn’t. A new study by scientists from Princeton University suggests that the material, called a quasicrystal, came from outer space in a meteorite. Moreover, the meteorite may be older than Earth itself. The finding indicates that materials that could never form naturally on Earth can form in space–which has scientists wondering what other materials are out there.

In a crystal, atoms are arranged in an orderly manner, with a regularly repeating pattern. The atoms in a quasicrystal also have an orderly arrangement, but they do not have a regularly repeating pattern. Scientists once thought that quasicrystals were an impossibility. In fact, when Daniel Shechtman, an Israeli engineer, reported his discovery of quasicrystals in 1982, the scientific community dismissed his findings completely. (In 2011, Shechtman won the Nobel Prize in chemistry for his discovery.) Several years after his discovery, other scientists made more quasicrystals in various arrangements. Then in 2009, scientists reported finding a naturally occurring quasicrystal in a rock from Russia’s Koryak Mountains.

Now Princeton scientists have reported that the Koryak quasicrystal appears not to have formed naturally on Earth after all. The rock apparently is the remains of a meteorite that formed 4.5 billion years ago, even before Earth had taken shape in the early solar system. In the rock sample, the scientists found a tiny grain of a mineral called stishovite, which occurs only at the kind of high pressure achieved in meteorite impacts and collisions. The quasicrystal was encased in the stishovite.

Both quasicrystals and crystals, such as these salt crystals, contain atoms that are arranged in an orderly pattern. But the atoms in quasicrystals do not follow the kind of repeating pattern found in crystals. (c) Charles Falco, Science Source from Photo Researchers

Many quasicrystals have practical uses. Certain quasicrystals can be particularly strong and hard. They are mixed with such metals as aluminum and steel and other alloys (mixture of metals) to increase a metal’s strength and hardness. Quasicrystals may also exhibit nonstick abilities, such as those found in the nonstick coatings on cookware.

Additional World Book articles:

• Mineral
• Symmetry

Oct. 7, 2011

The Nobel Prize in chemistry was awarded on September 5 to Israeli chemist Dan Shechtman of Technion–The Israeli Institute of Technology. Shechtman received the award for his 1982 discovery of quasicrystals. Quasicrystals are a previously unknown form of matter with a structure that scientists had believed was impossible.

Crystals are substances that are made of atoms arranged in an ordered repeating pattern. Almost all solid materials consist of crystals. The atoms of a quasicrystal are ordered but not repeating. It was later discovered that a quasicrystal’s structure closely follows a longstanding mathematical principle called the golden section. The golden section–or “phi”–is a special number approximately equal to 1.618; it appears many times in geometry and is often used in art and architecture.

Shechtman’s discovery, made while working at the U.S. National Institute for Standards and Technology, first met with strong resistance from fellow scientists. After more examples were brought to light, a belief in the existence of the quasicrystal gained wide acceptance. The Royal Swedish Academy of Sciences characterized Shechtman’s discovery as fundamentally changing the way chemists look at solid matter.

Additional World Book articles:

• Mineral
• Symmetry