In exploring how crystals form, researchers at New York University came across an unusual, rod-shaped crystal that hadn’t been identified before.
Zangenite. Image credit: Shihao Zang / NYU.
Crystals are solid materials made up of particles that arrange themselves in repeating patterns.
This process of self-assembly — ‘orchestrating order from chaos,’ as researchers describe it — was once thought to follow a predictable, classic pattern of growth.
But instead of always forming building block by building block, they are learning that crystals can grow through more complex pathways.
To study the formation of crystals, some researchers use crystals made up of little spheres called colloidal particles, which are tiny but much larger than the atoms that make up other crystals.
“The advantage of studying colloidal particles is that we can observe crystallization processes at a single-particle level, which is very hard to do with atoms because they’re too small and fast,” said New York University’s Professor Stefano Sacanna.
“With colloids, we can watch crystals form with our microscope.”
To shed light on how colloidal crystals form, Professor Sacanna and colleagues conducted experiments to carefully observe how charged colloidal particles behave in different growth conditions as they transition from salt water suspensions to fully formed crystals.
They also ran thousands of computer simulations to model how crystals grow and help explain what they observed in the experiments.
They determined that colloidal crystals form through a two-step process: amorphous blobs of particles first condense before transforming into ordered crystal structures, resulting in a diverse array of crystal types and shapes.
During these experiments, New York University Ph.D. student Shihao Zang came across a rod-shaped crystal that he couldn’t identify.
To the naked eye, it looked like a crystal previously discovered in the lab, but upon closer examination, the combination of particles was different and the tips of this crystal contained hollow channels.
He compared the unknown structure with more than a thousand crystals found in the natural world and still couldn’t find a match.
Turning to the computer modeling, the researchers simulated a crystal that was exactly the same, enabling them to study its elongated, hollow shape in even greater detail.
“This was puzzling because usually crystals are dense, but this one had empty channels that ran the length of the crystal,” said New York University’s Dr. Glen Hocky.
“Through this synergy of experiments and simulation, we realized that this crystal structure had never been observed before,” Professor Sacanna added.
They named the newly-discovered crystal L3S4 based on its composition, but began informally calling it ‘Zangenite’ at lab meetings, given that Zang discovered it.
“We study colloidal crystals to mimic the real world of atomic crystals, but we never imagined that we would discover a crystal that we cannot find in the real world,” Zang said.
The discovery of Zangenite creates an opportunity to explore uses for hollow, low-density crystals, and may pave the way for finding additional new crystals.
“The channels inside Zangenite are analogous to features in other materials that are useful for filtering or enclosing things inside them,” Dr. Hocky said.
“Before, we thought it would be rare to observe a new crystal structure, but we may be able to discover additional new structures that haven’t yet been characterized,” Professor Sacanna said.
A paper describing this research was published in the journal Nature Communications.
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S. Zang et al. 2025. Direct observation and control of non-classical crystallization pathways in binary colloidal systems. Nat Commun 16, 3645; doi: 10.1038/s41467-025-58959-0
