Dissolution Enables Dolomite Crystal Growth near Ambient Conditions

Crystals grow under supersaturated solutions. A mysterious counterexample is dolomite CaMg(CO₃)₂, an abundant sedimentary mineral that apparently cannot grow at ambient conditions, not even under highly supersaturated solutions. Using atomistic simulations, we show that dolomite initially precipitates a cation-disordered surface, where high surface strains inhibit further crystal growth. However, mild undersaturation will preferentially dissolve these disordered regions, enabling increased order upon reprecipitation. Our simulations predict that frequent cycling of a solution between supersaturated and undersaturated can accelerate dolomite growth by up to seven orders of magnitude. We validate our theory with in situ liquid cell TEM—directly observing bulk dolomite growth under supersaturation cycles. This mechanism explains why modern dolomite is primarily found in natural environments with <i>p</i>H or salinity fluctuations. More generally, it reveals that the growth and ripening of defect-free crystals can be facilitated by deliberate periods of mild dissolution.