PNNL

Abstract

Understanding rare-earth element (REE) mineralization mechanisms is essential for developing efficient separation strategies. Although the geochemical pathways that generate REE deposits are qualitatively known, quantitative links between specific conditions and mineralization outcomes remain limited. Herein, the repurpose laboratory REE hydrothermal synthesis data—originally collected for functional-materials fabrication—as a surrogate for studying mineralization with data-driven methods. The compiled 1,200+ hydrothermal reaction records and trained three machine-learning models—K-nearest neighbors (KNN), random forest (RF), and extreme gradient boosting (XGB)—to predict product elements and phases from precursors, additives, reaction conditions, and engineered features. Validation shows XGB achieves the highest accuracy. Feature importance indicates thermodynamic properties of cations and anions dominate model decisions. Correlations reveal positive relationships among precursor concentration, reaction time, pH, and temperature, consistent with classical crystallization behavior. XGB-based regressors are built to predict crystallization temperature and pH from precursor/product attributes. Performance is strongest when similar training examples exist, while accuracy declines for underrepresented reactions, notably REE carbonates and heavy-REE systems. Overall, the study shows that functional-materials datasets can illuminate REE mineralization and provide priors for exploration and processing. Expanding datasets with less-studied chemistries and conditions will improve generality and support deposit discovery and more efficient REE recovery.