River beach near the quarry
The path immediately upstream of Geosite A2 leads down to the Horoman River's dry riverbed, which is covered with oval or round stones of varying sizes that are said to resemble the round rice cakes offered to the gods at New Year. These stones reached the riverbed from the ridge of the Hidaka Mountains via the Horomankyo Gorge. They are made of peridotite, gabbro and other rocks that used to be located deep under the earth's surface. Although many of them have subdued colors when dry due to weathering and abrasion, viewing them in river water reveals the vivid colors of their mineral content.