The origin of the important rock-forming mineral dolomite remains uncertain, primarily because of the difficulty in the low-temperature precipitation of this mineral. The influence of solution variables such as sulfate ion concentration and magnesium concentration on the precipitation of the more readily precipitated mineral analogues of dolomite, BaMg(CO3)2 and PbMg(CO3)2, may provide insight into the precipitational environment of dolomite itself.
PbMg(CO3)2 was precipitated with equal facility from both sulfate-bearing and sulfate-free alkaline solutions in the temperature range 25–80 °C. The precipitation of this mineral analogue of dolomite from these solutions suggests that dolomite itself may precipitate from similar solutions without regard to the concentration of dissolved sulfate (SO42−). The precipitation of barite (BaSO4) in place of norsethite [BaMg(CO3)2] from sulfate-bearing solutions seeded with BaCO3 may have been caused by the relatively low thermodynamic solubility of barite rather than by a kinetic inhibition effect on norsethite precipitation due to the presence of dissolved sulfate.