Bead size: 9mm Inner diameter: 16cm Fluorite is named "Hotaru-ishi" (蛍石), meaning "firefly stone" in Japanese, because it emits a vivid fluorescent color when exposed to ultraviolet light or heat. Fluorite is called the "genius stone" and is believed to bring out clear thinking and enhance memory. It also helps to relieve mental fatigue, making it a good luck charm for those taking exams. In addition, it frees you from fixed ideas and suppressed emotions, enhancing free and innocent ideas and thinking ability. It is also a stone that shows the way and helps to find solutions for those who are troubled or lost.