Abstract
The gold decoration technique of electron microscopy was applied to as-grown (001) surfaces of sericite crystals collected from many localities in Hiroshima, Shimane and Yamaguchi Prefectures.
The specimens investigated exclusively exhibited growth spirals of either polygonal or circular forms with varying step separations. The morphological characteristics were critically analysed in relation to their modes of occurrence. It is demonstrated that the crystals directly precipitated from hydrothermal solutions in open fractures are characterized by circular growth spirals with narrower step separations, whereas those formed by hydrothermal metasomatism by polygonal growth spirals with wider step separations. The differences between the two are explained based on the recent understanding on spiral morphology.
