Epitaxy governs the location and orientation of nucleation in crystalline systems

Many geological and synthetic material processes, such as crustal metamorphism, alloy grain refinement and heterojunction fabrication require knowledge of the way in which crystals nucleate within a multiphase crystalline matrix. Nevertheless, a common set of rules that predict the location and orientation of nuclei growth in crystalline reactions has not previously been described. By studying the orientation relationships in 12 natural parent–daughter pairs with varying symmetry, we show that crystalline nucleation can be rationalized by a model of epitaxy in which the location and orientation of nuclei maximize coincident-site lattice bond interactions with a parental phase. We find that epitaxy is the default nucleation pathway in natural mineral reactions, which has implications for the self-organization of mineral systems, the kinetics of metamorphic reactions as well as the rheology of multiphase rocks. Broadly applied, our epitaxy model allows us to predict the microstructure of reacting crystalline systems based solely on the lattice structure and chemistry of constituent phases.