The Spelunker Glowstick is a light source that can be held or tossed a fair distance, similar to Glowsticks. However, unlike regular Glowsticks, Spelunker Glowsticks additionally highlight the location of nearby treasures in a 30 block radius around the glowstick with a slight yellowish glimmer. They are purchased from the Skeleton Merchant for 150 each.
Just holding a Spelunker Glowstick already reveals nearby treasure – it is not necessary to toss it.
Unlike the regular Glowstick, the Spelunker Glowstick disappears after expiring. It does not drop as an item and is therefore unreusable.
When held in a player's hotbar or held via Auto Select, the Spelunker Glowstick will expire after a seemingly random duration. This requires you to continuously buy Spelunker Glowsticks when using them, or amass a large stockpile in advance.
The treasure-revealing effect is visible for all players in multiplayer.
While the very similar effect of the Magic Lantern is permanent and does not require holding an item in the hotbar, its radius is smaller than the Spelunker Glowstick.
Since all treasures are highlighted with the same yellow glimmer, regardless of value, the Spelunker Glowstick becomes less useful as the game progresses. The Spelunker Potion will be more effective as it does allow differentiating different kinds of treasure.
While holding a Spelunker Glowstick from the inventory GUI with autopause off, the player can effectively make them last indefinitely, as they do not get consumed if held in the menu. Verify
The Spelunker Glowstick seems to have been made out of a bone.
It seems to be more bouncy than a regular Glowstick.