The relations between some properties and their sedimentary ages were examined for halloysites of weathering origin in Japan. Properties examined include content of halloysite in each specimen, stability of interlayer water, thermal behavior and ratio of infrared absorbance for bands at 3700 and 3620 cm^-1 (A₃₇₀₀/A₃₆₂₀). Halloysite contents were measured by DTA method. Stabilities of interlayer water were estimated from the existence probability of halloysite 10Å phase after the specimen was exposed to relative humidity of 30%(W³⁰_H). For this estimation, the X-ray diffraction profiles was simulated with mixed-layer models. For the examination of the thermal properties of halloysites temperatures of endothermic peaks at around 100 and 500°C and exothermic peak at around 1000°C, and slope ratios (a/b) of the endothermic peak at around 500°C on DTA curves were applied. With increasing age of sedimentation, following correlations are recognized as a general trend.(1) Halloysite contents in the specimens increases.(2) Stability of interlayer waters of halloysites decreases.(3) The peak temperatures and slope ratios of DTA curves of halloysites approach to those of kaolinites of disordered type.(4) The values A₃₇₀₀/A₃₆₂₀ in infrared spectra of halloysites approach to those of kaolinites. It is concluded that Properties of halloysites change and approach to those of kaolinites with increasing age of sedimentation.