What is the result when carbonic acid reacts with potassium feldspar?
Feldspar, a major constituent of most igneous rocks, reacts with carbonic acid to produce residual clay minerals plus dissolved ions of metals (potassium, sodium or calcium, depending on the type of feldspar). Here, for example, is the reaction by which potassium feldspar is converted to kaolinite, a clay mineral: 4KAlSi3O8 + 4H2CO3 + 2H2O → Al4Si4O10(OH)8 + 4K+ + 4HCO3- + 8SiO2 feldspar + carbonic acid + water → kaolinite + dissolved potassium and bicarbonate ions + dissolved silica Similar reactions affect sodium feldspar and calcium feldspar.