Equipment upgrade, each profession can upgrade specific items and you must use the mineral according to the rarity and tier of the item example:
Rare level item you must use a rare mineral to upgrade the item and each Tier has a maximum upgrade: Tier I = max +3 / Tier II = max +5 Tier III = max +10 / Legendary max +20.
Jeweler: It improves swords, shields and has a crafting that only that profession can do that is the improvement of a pet.
Elementist: Improves boots, gloves and has a crafting that only that profession can do that is the improvement of a pet.
Miner: It improves chest and helmet and has a crafting that only that profession can do that is the improvement of a pet.