Nontronite is the iron(III) rich member of the smectite group of clay minerals. Nontronites typically have a chemical composition consisting of more than ~30% Fe2O3 and less than ~12% Al2O3 (ignited basis).
Nontronite is a clay mineral rich in iron(III) and belongs to the smectite group. It typically has a chemical composition of more than 30% Fe2O3 and less than 12% Al2O3 (ignited basis).