Abstract
The growing stromatolitic structures which were composed of amorphous Mn minerals were found in Yunokoya hot springs, Gumma Prefecture, Japan. These stromatolitic structures are black and brittle. The form of these structures are hemispherical. Many bacteria that were coated with amorphous Mn minerals were found on these structures. It is suggested that the formation of these structures are related to the activities of bacteria coated with amorphous Mn minerals.
