Chlorite ($\mathrm{M}{\mathrm{g}}_5\mathrm{A}{\mathrm{l}}_2\mathrm{S}{\mathrm{i}}_3{\mathrm{O}}_{10}(\mathrm{OH}{)}_8$)

A group of sheet-silicate minerals; an idealized Mg-rich composition used in weathering models is $\mathrm{M}{\mathrm{g}}_5\mathrm{A}{\mathrm{l}}_2\mathrm{S}{\mathrm{i}}_3{\mathrm{O}}_{10}(\mathrm{OH}{)}_8$. Its alteration to gibbsite or kaolinite depends on dissolved silica and the magnesium-to-proton thermodynamic activity ratio.