Gensokyo/Dowsing Rod

The Dowsing Rod  is a Pre-Hardmode utility item. On use, it consumes one unit of the first ore found within the player's inventory (the inventory is searched left-to-right, top-to-bottom). If a deposit of that ore exists within a radidus of 50 tiles, a slow-moving, glowing projectile will spawn and guide the user towards the ore.

In addition, the Dowsing Rod can also be activated using gems rather than ore. In this case, it will lead the player towards any kind of gem, rather than only the one used to fuel it.

Trivia
The Dowsing Rod is a reference to the pair of dowsing rods wielded by Nazrin.