|Item class||Psynergy item|
|Special Equip Effect||Bestows Grind when equipped to a Venus Adept|
The Grindstone (グラインドのロツク, Rock of Grind?) is a Utility Psynergy item featured in Golden Sun: The Lost Age. It bestows the Grind Psynergy, and it can either remove massive brown rocks or lower them enough that they can be hopped across. Unlike all other Utility Psynergy items in the GBA duology, only Venus Adepts are able to equip this.
The Grindstone is particularly impactful on the progression of the plot in The Lost Age. It was originally found in some ruins by Lunpa the Righteous Thief during his treasure-hunting career, and it has remained in Lemuria with him since he originally came to Lemuria many decades ago. When Felix's party reaches Lemuria, they learn how necessary it is for the world's health for them to light the Elemental Lighthouses, which lie in the Great Western Sea.
What has prevented Felix from entering the Western Sea, however, is a rock formation that emerged when the continent of Indra shifted southwest to brush against lower Gondowan and northwestern Osenia - all as an outcome of the lighting of Venus Lighthouse. Lunpa entrusts the Grindstone to Felix so that he can resume his quest to light the Lighthouses and gain access to the Western Sea by using the Grind Psynergy on the rock formation. The removal of this rock formation with Grind subsequently allows for Karst, Agatio, and Alex to follow Felix into the Western Sea, and Isaac, Garet, Ivan, and Mia also follow their targets through where the formation once stood.