2:1 layer

See layer.

2:1:1 layer

Previously used to describe chlorite where a 2:1 layer plus an interlayer describes thesheet and layer configuration. This nomenclature is no longer in use, see Guggenheim et al. (2006) and references therein. Use 2:1 layer.
Cf., tetrahedral sheet, octahedral sheet, layer, interlayer material

2:2 layer

Previously used to describe chlorite where a 2:1 layer plus an interlayer was summed to two tetraheral sheets and two octahedral sheets. This nomenclature is no longer in use, see Guggenheim et al. (2006) and references therein. Use 2:1 layer.
Cf., tetrahedral sheet, octahedral sheet, layer, interlayer material