Phys.org  September 30, 2022 Researchers in Ireland studied the interaction between rare earth element (REE)-rich (La, Pr, Nd, Dy) aqueous solutions, dolomite (CaMg(CO3)2), and aragonite (CaCO3) at low temperature hydrothermal conditions (25–220 °C) to understand the formation of REEs. They found that the newly formed REE-bearing carbonates in La-, Pr-, and Nd-doped systems follow the crystallization sequence: lanthanite [REE2(CO3)3·8H2O] → kozoite [orthorhombic REECO3(OH)] → hydroxylbastnasite [hexagonal REECO3(OH)]. The interaction of Dy-bearing solutions with dolomite results only in the crystallization of kozoite [orthorhombic DyCO3(OH)]. However, experiments with aragonite reveal a two-step crystallization pathway: tengerite [Dy2(CO3)3·2-3(H2O)] → kozoite [orthorhombic DyCO3(OH)]. The temperature, […]