[Machine Translation] Listen to the history told by the stones. In volume 4, Ruri sets off on a topaz-collecting trip with her labmates after solving the mystery of where sapphires come from through repeated research. Ruri and her friends visit limestone caves and hot spring inns, where they encounter minerals unique to their travels! This is an authentic jewel hunt adventure in which the clues left behind by the earth are used to uncover the whereabouts of the minerals! In addition to the well-known newly illustrated columns, three bonus manga are also included.