Weathering of complex silicate minerals

The formula of the solid product (Al2Si205(0H)4) is that for kaolinite, an important member of the serpentine-kaolin group of clay minerals (Section 4.5.1). This reaction demonstrates incongruent dissolution of feldspar, i.e. dissolution with in situ reprecipitation of some compounds from the weathered mineral. 

Schematic representation of the anorthite chemical weathering reaction (Fig. 4.5) shows the edge of the anorthite crystal in contact with an H2C03 weathering solution. Natural crystal surfaces have areas of excess electrical charge at their corners and edges, usually because of imperfections (rows of atoms slightly out 

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