Pumices and ore of stones in a riverbed (base rock) assuming the spherical or disc shapes, were used unprocessed as materials, and many of these left the traces of being ground as signs of being used. |
球状または円盤状を呈する転石や河原石の原石(母岩)を加工せずにそのまま用いており、使用痕としては擦った痕跡ののこるものが多い。 |