Mechanically activated Estonian glauconitic sandstone potential as a raw material for K-fertilizer: Optimization of K release on a laboratory scale.

The Estonian Geological Survey is conducting research on phosphorite and associated resources during the period 2023-2025, one of the objectives of which is to assess the potential for beneficiation of associated mineral resources. Due to the geological structure of Estonia, there are several different rock bodies located above the phosphorite layer that could serve as potential raw materials. Above the phosphorite layer, there are construction limestone, U- and V-rich graptolite argillite, and K-rich glauconitic sandstone. Based on the principle that the Estonian resources must be managed sustainably and responsibly, Estonian phosphorite and the rock layers above it should be treated as a single complex mineral resource. However, the exploration of several associated resources is significantly lower compared to phosphorite. One of those potential resources is the glauconitic sandstone of the Leetse formation, which contains greenish K- and Fe-rich clay mineral glauconite. Due to the complex structure of the mineral, the chemical composition of glauconite varies greatly, and in some cases K contents can reach up to 7%. The main objective of the work is to find an optimal scheme for the mechanical activation of glauconite on a laboratory scale. The objectives of the work can be divided into three parts: (1) to assess the effect of mechanical activation on the structure of glauconite grains, (2) to determine the chemical composition of mechanically activated glauconite, and (3) to evaluate the leaching of various beneficial and/or potentially harmful components.