The Sparkling Stone (Japanese: かがやくいしSparkling Stone) is a Key Item introduced in Generation VII. They are gifted to worthy Trainers by the tapu. It is the raw material needed to create a Z-Ring or Z-Power Ring. According to Professor Kukui and Lillie, Sparkling Stones are actually the parts of Necrozma's body that were lost due to the actions of the Ultra Recon Squad's ancestors. These parts then came to Alola after passing through an Ultra Wormhole.
The player receives a Sparkling Stone from Tapu Koko in recognition of their bravery in protecting Nebby from a swarm of wildSpearow. After the player defeats Hau for the first timeSM or simply returns to Iki TownUSUM, Hala recognizes the stone, and upon realizing that the player has been recognized by the guardian deity of Melemele Island, offers to refine it. The player receives the finished product, a Z-RingSM or Z-Power RingUSUM, after completing the ceremony battle with Hau.
Another, unobtainable Sparkling Stone is given to Hapu by Tapu Fini when the former is made the island kahuna of Poni Island. She later fastens it into her own Z-RingSM/Z-Power RingUSUM. This Sparkling Stone is colored brown, unlike the whiteSM/blackUSUM one the player received earlier.
In The Wild Full-Power Pose of Fire, Kiawe is revealed to own a Z-Ring, which he received as a Sparkling Stone from Tapu Lele five years prior to the Sun, Moon, Ultra Sun & Ultra Moon chapter. In order to prevent Sun from using Inferno Overdrive against him again, Gladion had his Type: Null shatter Kiawe's Z-Ring when the latter attempted to lend it to Sun, leaving only the Sparkling Stone intact.
