Occurrence of imogolite as gel film in the pumice and scoria deds of western and central Honshu and Hokkaido

Since its first discovery in 1962 (24, 25), imogolite has been known to occur widely in ando-sols from subfrigid to temperate to tropical regions(1, 2, 3, 6, 7, 9, 14) and, peculiarly as gel films, in certain weathered pumice beds of Japan (11, 23). Its morphology and chemical and mineralogical properties have been investigated fairly well and the investigations have reached the 'stage where its structural models can be hypothesized (13, 16, 19, 20, 26). Relatively little attention has been paid, however, to the mechanism of its formation and to its genetic relationship to other clay minerals(18). Elucidation of these points will be very important in establishing imogolite as a member of weathering sequence in soils, and for this to be done will be needed much more extensive study of its distribution, clay mineral suits associated, environmental conditions in soils, etc.