礫岩の選択風化とつぼ石

抄録

Tsubo-ishi, a weathered pebble having an iron-rich spherical crust on the surface and clay materials in the core, was collected in a conglomerate found in the Shemmei Pass area, Gifu Prefecture. The conglomerateis composed of pebble sized and small fragments of chert and embedded in a matrix of clay materials. Occasional pebbles of mudstone, sandy tuff and granite are also found but they are usually weathered and changed to clay. On the other hand, the crust of Tsubo-ishi is composed of goethite and chert granules, whereas the core is dominantly mixture of kaolin minerals with minor mica clay minerals and quartz. This report shows some mineralogical data on Tsubo-ishi and describes its mechamism of formation.