A′KF diagram

A triangular diagram showing the simplified compositional character of a metamorphic rock by plotting molecular quantities of the three components: A′=Al2O3 + Fe2O3 - (Na2O + K2O + CaO); K=K2O; and F=FeO + MgO + MnO. A′+K+F (in mols) are recalculated to 100%; the diagram is used in addition to the ACF diagram when K minerals require representation. Cf: AFM diagram.