Replacement dolomitization of calcite is a chemical process where dolomite comes to occupy the spatial position and volume of calcite through simultaneous dissolution of calcite and precipitation of dolomite without effecting a volume change in the crystalline portion of the rock. Dissolution and precipitation occur adjacent to one another in conjunction with a narrow aqueous boundary film width which separates the dolomite growth surface from the calcite dissolution surface. The primary condition of replacement is that the volumetric rate of calcite dissolution at the actual replacement site exactly equals the volumetric rate of dolomite precipitation even though the precipitation-dissolution rates in the adjacent pores may differ widely. The volumetric equality of these rates is established by the growing dolomite crystal exerting a linear force of crystallization on the microenvironment of the replacement site. This force increases the pressure within the aqueous boundary film which in turn retards dolomite precipitation and enhances calcite dissolution. The pressure established by this force is that pressure where the thermodynamic potential for dolomite precipitation exactly equals the thermodynamic potential of calcite dissolution times the ratio of the molar volume of dolomite to that of calcite. The kinetic rate of replacement in terms of volume per unit time is proportional to a function of the dolomite thermodynamic potential and inversely proportional to functions of the pressure developed within the boundary film and the size of the growing dolomite crystal. Replacement calcitization of dolomite is an analogous process differing only in direction of the component reactions.