抄録
Kaolin minerals derived from pumice tuff by weathering are mainly composed of hydrated halloysite. From the studies of X-ray powder reflection and d. t. a., these clay minerals have low crystallity and are mixed with allophane or gel-like substances. The shapes of these specimens are special and classified into the following types: (a) tubes, hexagonal plates and radial aggregates of plates, (b) tubes and redial aggregates of tubes, (c) polyhedral or spherical particles, (d) sugar-plum like grains, jutting out radially from the grains.
From this study the process in the growth from allophane or gel-like substance to hydrated halloysite can be postulated.
Furthermore, the presence of hexagonal plates on type (a) may be explained by the development of Bates' idea for a rolled shape on ordinal halloysite.
