Formation of dolomite analogues at ambient conditions


Dolomite analogues are an interesting group of carbonate minerals and synthetic compounds with structures similar to that of dolomite and varied cationic compositions. Some of these dolomite analogues are relatively easy to synthesise from aqueous solutions (e.g. norsethite (BaMg(CO3)2) and PbMg(CO3)2), whereas the formation of others is strongly inhibited (e.g. SrMg(CO3)2 and CdMg(CO3)2). Such a difference in the crystallisation behaviour of compounds with dolomite-like structure gives us the opportunity to investigate the reaction mechanisms which may also control dolomite crystallisation in nature. Recent investigations on the formation of dolomite-analogues at ambient conditions have revealed that: (i) when the formation of these analogues occurs, their crystallisation is always preceded by the formation of amorphous and/or crystalline precursors; (ii) such precursors can be transformed into highly ordered dolomite analogues via dissolution-crystallisation reactions; and (iii) the kinetics of the identified crystallisation-dissolution reactions are strongly dependent on both the concentration and the ratio of cations (e.g. Ba:Mg, Pb:Mg) in the aqueous solutions. In this chapter, we discuss the implications of experiments on the formation of dolomite analogues for a better understanding of dolomite crystallisation in aqueous environments at ambient conditions.

Dolomite: Formation, characteristics and environmental impact