The Fe-rich member of the chlorite group with a composition of ideally Fe²⁺₅Al(Si₃Al)O₁₀(OH)₈. There may be considerable substitutions of Mg, Fe³⁺, and Al for Fe²⁺. The common polytype is the IIb form, a one-layer form. Chamosite is an important constituent in oolitic and sedimentary iron formations and may be found as grain coatings in sandstones.
See chlorite