Long spacings as 29., 6 Å and 26., 6 Å are confirmed from certain clays from Japan, which have very complicated clay mineral compositions including kaolin minerals, chlorite, sepiolite and montmorillonite., Each long can be explained by a regular interstratification between two kinds of lattices selected from the following ones: montmorillonite lattice with the cell height of 15., 4 Å, a magnesian chlorite of 14., 5 Å, sepiolite with 12., 7 Å, and a new lattice of 14., 0 Å; the last is a regular interstratification of gibbsite and silicate (pyrophyllite unit) layers., This new lattice is proposed to explain the spacing and all other mineralogical properties of the clay., Thus the 29., 6 Å spacing agrees well with that of a regular mixed-layer lattice configurated by the 15., 4 Å and 14., 0 Å cells, and the 26., 6 Å spacing with a regular mixed-layer lattice by 12., 7 Å and 14., 5 Å cells., These long spacings are liable to be found in a clay in which several kinds of clay minerals co-exist, and such a complex clay tends to be found in special conditions, such as a boundary area between two different kinds of altered zones, and or an area affected by successive hydrothermal alteration.,