Biogenic filamentous fabrics in green colored moss agates within miocene volcanic rocks in Japan and the associated formation of celadonite

Moss agate is a variety of agate characterized by the presence of black, green, or red filamentous fabrics that resemble vegetation such as moss, algae, ferns, and other plant-like forms. These fabrics occur within chalcedony, opal, or other silica minerals across various geologic periods. Traditionally, these filamentous fabrics have been regarded as the result of inorganic precipitates. In this study, we investigated filamentous fabrics within typical green-colored moss agates collected from Miocene rhyolitic pyroclastic rocks at Bodai (Komatsu, Ishikawa) and from Miocene andesites or andesitic pyroclastic rocks at Imakane (Kunnui, Hokkaido), Japan. Our analyses demonstrate that the filamentous fabrics in the green moss agates are of biogenic origin. The biogenic materials had been subjected to corrosion, after which the resulting voids were filled by celadonite precipitates. In certain portions of these filamentous fabrics, carbonaceous matter, representing the remnants that resisted corrosion, was detected. These findings suggest that some filamentous fabrics observed in green-colored moss agates worldwide should be reconsidered as being of biogenic origin. Consequently, such filamentous fabrics of biogenic derivation warrant investigation as potential "fossils" within the context of Earth's history.