This is a chest ornament from the Jōmon period, which lasted from around 11,000 BC to the 5th century BC. It seems the cord was threaded through the round hole at the top. These ornaments usually have cylindrical shapes that taper at the top and bottom, though this example has a trapezoid shape similar to an axe head. The rounded edges are the result of careful polishing. The ornament yields a beautiful semi-translucent green hue when placed under light. It is made of jade. In Japan, jade production was limited to the basins of the Hime River and Ōmi River in the southern part of Niigata, so it was an extremely precious stone at that time. As such, chest ornaments were only found in a few Jōmon settlements. Even then, the settlements would only have around one such object and it would only be worn by select individuals. This jade axe was found in Tochigi prefecture, over 200 kilometers away from its production site in Niigata. Its owners either travelled to Niigata to fetch the jade themselves or they obtained it through trade. It is thought there were large trading settlements in the center of the regions where objects like this were found.