Mineral dendrites are an example of a pattern that forms in rocks when they are infiltrated by Mn-rich hydrothermal fluids. These fluids interact with oxygenated fluids within the rock matrix, leading to the formation of manganese oxide, which subsequently precipitates and forms intricate patterns. Bacteria can catalyze manganese oxidation reaction by at least 2-3 orders of magnitude and hence their presence can play a significant role in the formation and growth of manganese precipitates. We hypothesize that presence of Mn-oxidizing bacteria can also trigger band formation in the growing dendrites, which is observed in some natural structures.

We investigate this process using numerical simulations and analyze dependence of dendrite morphology on various physical parameters such as initial concentrations of manganese ions and oxygen molecules, reaction rates, nucleation thresholds, and surface energy. We have compared numerical results with experimental data on 3D dendrites in zeolites btained using X-ray microtomography, which has revealed the presence of a banded pattern. Simulation results and experimental data agreement allows us to infer the presence of microorganisms during formation. We have compared numerical results to morphologies of the real systems with the aim of reconstructing hydrochemical conditions prevailing during their growth.