ABSTRACT
Extensive areas of karst evolve in carbonate rocks (limestones and dolomites), and sometimes in evaporites, which include halite (rock salt), anhydrite, and gypsum. Figure 14.2 shows the
global distribution of exposed carbonate rocks. Limestones and dolomites are a complex and diverse group of rocks (Figure 14.3). Limestone is a rock containing at least 50 per cent calcium carbonate (CaCO3), which occurs largely as the mineral calcite and rarely as aragonite. Pure limestones contain at least 90 per cent calcite. Dolomite is a rock containing at least 50 per cent calcium-magnesium carbonate (CaMg(CO3)2), a mineral called dolomite. Pure dolomites (also called dolostones) contain at least 90 per cent dolomite. Carbonate rocks of intermediate composition between pure limestones and pure dolomites are given various names, including magnesian limestone, dolomitic limestone, and calcareous dolomite.
