Gakusanjin's crystallized yōki

was crystals that Gakusanjin created from his own yōki. he allowed Inuyasha and his friends to take one of them in order to track the Fuyōheki and return it to him. The aura around the crystal would disappear if it was even close to the Fuyōheki. Miroku held on to the crystal until it was stolen by Mōryōmaru. Kagura also obtained a crystal and gave it to Sesshōmaru so he could find and destroy Naraku's heart that was in possession of the Fuyōheki.

妖氣的結晶