During dissolution in acid the Mg2þ ions are replaced by
hydrogen ions, yielding Si(OH)4 monomers and Mg2þ
ions in solution. The reaction results in a large reduction
of acidity. Most investigators have reported a reaction
order of approximately 0.5 for the hydrogen ion, i.e. the
logarithm of the reaction rate is proportional to )0.5 pH
(Rosso and Rimstidt, 2000). The strong pH dependence
means that forsterite goes from being a virtually inert
mineral to a fast weathering mineral within a rather
limited pH range