Scientists have long worked to understand how crystals grow into complex shapes. Crystals are important in materials from skeletons and shells to soils and semiconductors, but much remains unknown about how they form.

Now, an international group of researchers, including a Virginia Tech geoscientist, has shown how nature uses a variety of pathways to grow crystals that go beyond the classical, one-atom-at-a-time route.

The findings, published Thursday in the journal Science, have implications for decades-old questions in science and technology regarding how animals and plants grow minerals into shapes that have no relation to their original crystal symmetry and why some contaminants are so difficult to remove from stream sediments and groundwater.

“Researchers across all disciplines have made observations of skeletons and laboratory-grown crystals that cannot be explained by traditional theories,” said Patricia Dove, a University Distinguished Professor and the C.P. Miles Professor of Science in the College of Science at Virginia Tech. “We show how these crystals can be built up into complex structures by attaching particles — as nanocrystals, clusters, or droplets — that become organized into complex shapes. Many scientists have contributed to identifying these particles and pathways to becoming a crystal — our challenge was to put together a framework to understand them.”

The results emerged from discussions among 15 scientists working in geochemistry, physics, biology, and the earth and materials sciences. At home, these researchers conduct lab experiments, investigate animal skeletons, study soils and streams, or use computer simulations to visualize how particles can form and attach.

The international group met for a three-day workshop in Berkeley, California, sponsored by the Council on Geosciences of the Office of Basic Energy Sciences of the U.S. Department of Energy.

“Because crystallization is a ubiquitous phenomenon across a wide range of scientific disciplines, a shift in the picture of how this process occurs has far-reaching consequences,” said materials scientist and physicist James De Yoreo at the Department of Energy's Pacific Northwest National Laboratory. “Moreover, because we largely show a community consensus on this topic, the study has the potential to define the directions of future research on crystallization.”

In animal and laboratory systems alike, the process begins by forming the particles. They can be small molecules, clusters, droplets, or nanocrystals. All of these particles are unstable and begin to combine with each other and with nearby crystals and other surfaces.