In two years of being online, 7,000 people from 89 countries have accessed Professor Chen Zhu’s public database of thermodynamic properties of rare-earth and other critical minerals; the Earth and Atmospheric Sciences Professor and his team have added nearly 200 data points about commonly mined minerals.
Rare-earth elements are a set of commercially important but hard-to-extract heavy metals found in the Earth’s crust. They have permanent magnetic properties, making them a hot commodity for electric vehicles, wind turbines, cell phones, and other high-tech products. Their name comes not from their scarcity (the U.S. Geological Survey describes them as “relatively abundant”) but from the difficulty of separating them from the ores in which they occur.
Zhu, a professor in the Department of Earth and Atmosopheric Sciences within the College of Arts and Sciences at Indiana University Bloomington, along with postdoctoral research associate Ruiguang Pan, recently authored a publication in the open-access journal Minerals that focuses on rare-earth element phosphates found in ores. “If you can mine it and make a profit, it’s an ore deposit. If you can’t, it’s just a rock,” said Zhu.
Before embarking on a large-scale extraction, companies and environmental agencies often use geochemical models to understand where to mine, which methods to use, and how to mitigate environmental impacts. The quality of these models relies on the quality of their data inputs, something that Zhu noted was lacking in the field.
“[Thermodynamic data] are scattered in different literature: some in geology, a lot in materials science or ceramics,” said Zhu. “You have all different groups using different ways to measure. Our group’s contribution is: ‘let’s evaluate these data and see what data are consistent with each other’ and then ‘this is the set of data we recommend you can use’,” he said.
Standardizing the data wasn’t easy. Funded by the Department of Energy, the group amassed data published between 2005 and 2024 about the energy contained within rare-earth minerals. They found that the reported values for an important property, Gibbs free energy of formation (ΔG°f), varied widely. In geochemical models, this parameter is used to calculate solubility and fluid-rock interactions, so getting it right is crucial.
Zhu and colleagues used a series of mathematical equations to predict Gibbs free energy values and compared these to experimental reports. They zoomed into these minerals at the fundamental level, taking into account variables like ionic radius and crystal structures. The group used these results to recommend a set of standardized, internally consistent thermodynamic properties to be used in geochemical modeling. In addition to the data published in the journal Minerals, they have compiled thermodynamic data for nearly all other known rare earth minerals, which they will present at the Goldschmidt conference in August.
The group added these data to SUPCRTBL, an open-source database and program originally created by researchers at the University of California - Berkeley that Zhu has been improving for nearly a decade.
For the past four years, Zhu’s group has partnered with undergraduate students from the Luddy School of Informatics, Computing, and Engineering to bring the databases and computer programs online and upkeep the backend of this cyberplatform. “The Luddy students contribute tremendously to this project. Most geochemists, including myself, lack 21st century coding skills” said Zhu. “We are so forturnate to have bright and extremely responsible undergraduate students who have run a geochemical modeling cyberplatform for years that the world has relied on for teaching and research.”
“I think what’s great is, you know, we are using IU’s superb IT resources to connect different fields together to have students participate. And not only do they participate, they are actually interested in those projects and have contributed to a different field at the scale beyond their imagnination,” added lab manager Lei Gong.
To Zhu, involving students is crucial for the revival of the field of critical minerals. The U.S. once led the world in research, education, and exploration of critical minerals, but the field and educational programs largely diminished in the 1990s. “We need to revive the curriculum and train the next generation of Earth scientists who have strong environmental ethics and are competent in meeting this need for green energy,” said Zhu.
Paradoxical as it may seem, renewable energy sources like wind and water turbines rely on rare-earth elements to function. And as long as they do, Zhu hopes that his group’s basic science can help inform more sustainable mining practices. “We need to provide a scientific foundation for innovation and discovery,” he said.