Dissolved ammonia catalyzes proto-dolomite precipitation at Earth surface temperature

•Inorganically-produced proto-dolomite precipitated successfully at normal temperatures.•Proto-dolomite precipitated at 40 °C exhibited a certain degree of ordering.•Dissolved ammonia accelerated the dehydration of Mg[(H2O)6]2+. Marine carbonate rocks are the major reservoir of carbon through CaCO3 and CaMg(CO3)2 precipitation extracting CO2/HCO3- from the atmosphere/oceans; hence dolomite is one of the major sinks in the global carbon cycle. Most ancient dolomite has been considered as mainly precipitated under Earth surface conditions. Previous studies have demonstrated that microbes can mediate dolomite formation. However, the “microbial dolomite” model is not sufficient to explain the dolomite that shows no or little evidence of a microbial origin. Although attempted for decades, the synthesis of inorganically-produced dolomite at normal temperatures (