Nomenclature for stacking in phyllosilicates: report of the Association Internationale pour l'Etude des Argiles (AIPEA) nomenclature committee for 2008

Two recommendations are made in regard to the nomenclature for stacking in, first 2:1 and then 1:1, phyllosilicates. The first recommendation is meant to eliminate ambiguity in use of the adjective 'interlayer' for 2:1 layer phyllosilicates. It is recommended that the layer displacement for 2:1 layers be defined as the sum of the intralayer displacement and the interlayer displacement. Intralayer displacement and interlayer displacement are discussed and exactly defined. The term 'structure unit' of Bailey (1980) is the total assemblage of the layer plus interlayer. For 1:1 layers the layer displacement can also be defined as the relative lateral displacement between adjacent layers. However, Bailey (1988) termed this displacement 'interlayer shift'. To avoid confusion and to maintain parallelism with 2:1 layers the term 'layer displacement' should be used, instead of 'interlayer shift'. The terms 'adjacent layer displacement' and 'layer shift' are equiv. to 'layer displacement'.