Listen closely to the history told by stones. After extensive research, Ruri has unraveled the mystery of the sapphire mines. In volume 4, she embarks on a journey to collect topaz with her friends from the lab. Visiting limestone caves and hot spring inns, Ruri and her companions encounter minerals unique to their travel destination! A genuine jewel hunt adventure that uncovers the locations of minerals based on clues left by the Earth! In addition to familiar newly illustrated columns, there are also 3 bonus manga included.