Numerical analyses of water-rock interaction (metasomatism) require the precipitation/dissolution kinetics quite different from that of a single mineral in hydrothermal solutions: 1) in replaced zones of bimetasomatism, there may be a kinetics obstructing mineral precipitation in stationarily oversaturated conditions, and 2) at replacement fronts of infiltration metasomatism, precipitation/dissolution rates of reacting minerals may be controlled by the lowest concentration component notwithstanding their reaction surfaces when the concentration of the component is extremely lower than the others.