If you look closely at some items, they have the word artifact in the last column. What this means is they can not be destroyed, except for the Jewels of Power. Below is a list of the Artifacts that can be found in the game:

Xantan's Ring: Used to upgrade your weapons

Rotting Wooden Key: Used to open a locked door in the Ruins Tower

Silvered Horn Key: Same as Rotting Wooden Key

Jeweled Crystal Key: Same as Rotting Wooden Key

Staff of Ni-Tas: Used to upgrade your weapons

Rusty Medallian: Becomes Keladrian Medallian after polishing it

Clouded Gem: Becomes Coruscating Gem after repairing it

Coruscating Gem: Used to upgrade your weapons

Keladrian Medallion: Used to defeat Faleinn upon battle

Key to the Two Rings: Used to get into the Two Rings