Obsidian is a very hard stone that can be worked to produce a sharp edge, so it was widely used to make stone tools from the Paleolithic period onwards. Found only in volcanic regions, obsidian was a key item of exchange during the Neolithic period. Significantly, obsidian samples from different regions have different chemical properties, so analysis of obsidian artifacts can reveal important details about the cultural exchange of the past. For example, obsidian artifacts discovered along the southeastern coastline of Korea were found to have originated in the Kyushu region of Japan, showing that the two regions engaged in cultural exchange during the Neolithic period.