Mineralogical studies on todorokite and birnessite from the todoroki mine, Hokkaido

Abstract

Todorokite and birnessite from the Todoroki mine, Hokkaido, Japan were studied by electron micrographs, X-ray and differential thermal analysis. Electron micrographs of todorokite show the crystals to be thin plates flattened on {001}. Many of the plates are broken into narrow laths or blades which are elongated parallel to the b axis. It appears as though the crystals have two perfect cleavages parallel to {001} and {100}. D. T. A. curve of todorokite is characterized by a endothermic peaks at 104°C, 280°C, 480°C, 508°C, 545°C and 680-880°C. D. T. A. curve of birnessite is characterized by a endothermic peaks at 120°C, 260°C, 540°C and 680°C. Electron micrographs of birnessite show the crystals thin plates and needle shape. X-ray powder pattern data correspond to thore which were obtained by other writers.