Geo

Geo is an NPC in the Dwarven Mines that explains the use of Gemstones. Directly next to him you can find the Gemstone Grinder where items and armor can be upgraded using Gemstones.

Gemstone Grinder
the Gemstone Grinder next to Geo, players can apply Gemstones to specific items. These provide specific stats for each Gemstone.

Tip: Clicking on the redstone torch will bring up the Gemstone Guide, showing what items can have gemstones applied to them