Earthworms decompose ingested earth materials through interactions of small molecular organic acids with minerals to accelerate soil weathering. This process is difficult to be assessed in vivo because the average residence time of soils inside earthworm gut is on the scales of 12 hours, too short for minerals to exhibit sizable and visible dissolution features. In present study, earthworm weathering of calcite (CaCO₃) and K-feldspar (KAlSi₃O₈) is investigated in vitro using a mixed organic acid solution at pH 7 mimicking the composition and pH conditions of gut fluid. Experimental results showed that the dissolution rates experienced one order of magnitude increase relative to that in pure water, suggesting the occurrence of organic ligand-promote weathering. The observed correlation of dissolved cation concentrations to mineral particle sizes for calcite but not feldspar suggests the former dissociates directly in accordance with the stoichiometry while the latter dissolves following an incongruent pathway. Based upon this understanding, we further examined the dissolution kinetics using the initial rate method for feldspar and the shrink core model in conjunction with the Hixson-Crowell equation for calcite. The theoretical analyses indicate feldspar dissolution initiates as K⁺ release from mineral surfaces whereas calcite weathering is chiefly limited by the rate of reactant diffusion in solutions. These findings are in agreement with the known mechanistic framework for calcite and feldspar dissolution, but showcase the importance of ligands, instead of protons, to earthworm digestion of minerals in vivo.