A matter of discovery

May 6, 2019

The Siberian tundra in summer is mosquitoes, stormy mountain ranges, rushing rivers, giant bears and miles and miles of roadless muck, all under the midnight sun.

Physicist Paul Steinhardt’s book about his search for a new kind of matter begins, not with descriptions of laboratories where scientists search the submicroscopic realm for unique arrangements of atoms, but in remote eastern Russia.

The book reads like a good adventure story, not a dry scientific treatise. However, a careful reader will emerge with a basic knowledge of crystallography and mineral formation.

The author of The Second Kind of Impossible: The Extraordinary Quest for a New Form of Matter is now a professor at Princeton University. His search began some 40 years ago, and not in the wilds of Siberia.

For decades, Steinhardt’s search was confined to mathematical models as he worked with colleagues at various prominent East Coast universities. His question: Have scientists discovered all the ways that atoms can arrange themselves to make matter?

For centuries, scientists have accepted as fact that when liquids cool into crystals, atoms arrange themselves in predictable, repeating patterns. Carbon atoms form specific patterns to make diamonds and graphite.

In diamonds, each carbon atom is bonded to four other carbon atoms, making a super-hard mineral. Every diamond on every person’s finger throughout the world has one carbon atom connected to four others.

In graphite, each carbon atom is bonded to three other carbon atoms in a flat sheet. From one end of your pencil to the other, the graphite contains one carbon atom connected to three others, making sheets of molecules that peel off as you write.

The arrangement of atoms in quartz, lead, copper, salt, are all predictable, known as periodic.

Steinhardt wondered: Could there be minerals that weren’t periodic?

Impossible, said physicists, chemists and geologists.

He explains in his book that there are two kinds of impossible. The first is making a perpetual-motion machine or getting along with your in-laws round-the-clock. The second involves contradicting long-held assumptions that aren’t necessarily true. Sailing around the world in the days when people believed in a flat Earth might be an example.

Those studying minerals and industrial materials know that they are made up of symmetrical building blocks of atoms. Each kind of building block can be rotated to a certain angle and look identical to what it did before rotation. Some can be rotated twice, some three times, some six times, some only once, before they make a complete circle — they have onefold, twofold, threefold or sixfold symmetry. These building blocks repeat over and over again to make different kinds of matter.

Since the 19th century, experts have said that fivefold symmetry is impossible. They proved it by examining thousands upon thousands of minerals, from across the Earth and under the crust.

With mathematical calculations, by building models and by collaborating with experts in academia, Steinhardt and his co-researchers predicted that fivefold symmetry is possible, and that crystals can form in patterns that don’t repeat periodically. He invented the name quasicrystal.

In the early 1980s, Israeli materials engineer Dan Shechtman discovered fivefold symmetry in a man-made substance composed of aluminum and manganese. These artificial quasicrystals have become important in industry, and Shechtman won the Nobel Prize in chemistry.

Can quasicrystals be found in nature after all, Steinhardt wondered? He searched mineral collections in museums and universities with no luck. He put out a query to scientists across the world, and heard from the Italian mineralogist Luca Bindi, of the Natural History Museum at the University of Florence. The scientists collaborated, with Bindi finding a specimen in his collection that looked like it might contain a quasicrystal.

The specimen was a tiny chip containing a very rare mineral called khatyrkite, named after the Khatyrka river in eastern Siberia. This sample contained several copper and aluminum alloys and was the size of a small coin. Bindi found fivefold symmetry in one of the minerals associated with the khatyrkite — they named this quasicrystal icosahedrite. The experts had said it was impossible for any mineral to have fivefold symmetry.

Steinhardt and Bindi began a fruitful collaboration. They wanted to find out where the sample was found and how the rock had formed. There was little of the Florence sample left to study, as Bindi had sliced up most of it during his investigations.

Their search for more samples of khatyrkite had many steps, from a secret mineral collection in Italy, through a Russian smuggler, to a 1979 expedition to find platinum in Siberia. They tracked down Valery Kryachko, who had been on that expedition. He had collected not platinum, but aluminum and copper-based minerals in a clay layer on an extremely remote stream in the tundra, north of the Kamchatka Peninsula, just west of Alaska. That mineral ended up in Florence.

Why was a quasicrystal found in remote Siberia, and nowhere else on Earth? Not being an earth scientist, Steinhardt had to learn about mineral formation and geologic processes. He turned to Lincoln Hollister, a geosciences professor at Princeton who has extensive field experience in British Columbia, Alaska, California and Northern New Mexico.

Together, with a group of other geologists, they pondered the origins of khatyrkite and the minerals associated with it. Some experts said it came from deep within the Earth. Others said it couldn’t be a naturally occurring rock and might be a hoax. Steinhardt believed the specimen was part of a meteorite that formed in space some 4.5 billion years ago and landed on Earth at the end of the last ice age. It became clear that Steinhardt would have to mount an expedition and return to Siberia in order to collect more samples.

He is a lab scientist, not an explorer. For him mounting an expedition was challenging. Colleagues said he would never obtain funding, but he found a private donor. Experts told him that it would be impossible to find another meteorite sample in Siberia’s vastness.

Yet Steinhardt and Bindi set off into the wilderness in July 2011, accompanied by several U.S. scientists and a Russian expedition team that included Kryachko. Several colleagues of Steinhardt’s geology mentor Lincoln Hollister went along.

In two large vehicles that looked like a bus on top of military tank treads, they set off across the roadless tundra toward a small stream at the base of Koryak mountains where the sample had been discovered.

Their campsite could not have been more remote. The team battled mosquitoes, rain and wind, but the legendary Siberian bears kept their distance.

It would have been far easier to find a needle in a haystack than to find tiny grains of a quasicrystal in the Siberian tundra. The searched local clay samples for extraterrestrial grains. Field geologist Chris Andronicos (whose family has ties to Pojoaque Pueblo) mapped the area for clues as to whether khatyrkite was formed on earth or in space.

Against all odds, Steinhardt’s expedition was successful. His team brought back several samples that helped convince other scientists they had found a new kind of matter. Bindi and his colleagues went through the specimens brought from Siberia, identifying three different, naturally occurring, types of quasicrystal. Extensive study showed these minerals had come to earth in a meteorite.

The team had attained the second kind of impossible; they had brought back proof of a new kind of matter because they challenged the conventional wisdom that said it couldn’t exist.

Of course, there are still doubters, including a group of Russian scientists who believe the samples are man-made.

The chronicle of Steinhardt’s discoveries was published by Simon & Schuster this year. He will be at Bookworks in Albuquerque at noon Saturday to sign copies.

Along with his colleagues Bindi and Hollister, the author will be in New Mexico during May, touring the geology of the northern part of our state.