components dissolve. The alumino silicate minerals are the great example of the incongruent class, releasing Na+, K+, HCO-, etc. ions in reaction with J water but retaining most of their atoms in re-ordered solids such as kaolinite. The karst minerals are all congruent in normal conditions. Incongruent solution of dolomite and precipitation of calcite may occur in some exceptional conditions mentioned later. The sample of congruent minerals in Table 3. 1 contains all the common elements of crustal rocks except Fe, and furnishes a majority of the common dissolved inorganic species. The range...