|Debuff tooltip||Losing life and slowed movement|
The underworld is made of a material called hellstone. It's perfect for making weapons and armor.
— The Guide
Hellstone is an ore that can be found in The Underworld. Mining it requires at least a Nightmare/Deathbringer Pickaxe, and it cannot be mined with explosives Pre-Hardmode. Hellstone in the Underworld emits a faint glow and releases a half-tile of lava when mined. Hellstone tools are among the most powerful that can be acquired in Pre-Hardmode, rivaled only by two fish themed tools that can be caught from fishing, the Sawtooth Shark, Rockfish and Reaver Shark.
Hellstone inflicts the Burning debuff on players who touch it. Items that protect the player from fire blocks (including the Obsidian Skull, Obsidian Shield, Obsidian Horseshoe, Obsidian Water Walking Boots, Lava Waders, and Obsidian Skin Potions) will allow players to touch it without incurring fire damage. NPCs and Enemies do not receive damage from Hellstone.
- Hellstone will not create lava if mined outside of the Underworld.
- The Spelunker buff will not light up Hellstone, and the Metal Detector (and upgrades) will also not show Hellstone nearby. However, the Dangersense buff will. Nevertheless, it can be found easily due to the sparks it produces and its contrast to the Ash Blocks.
- In Hardmode, Hellstone can be destroyed with Dynamite and Bombs.
- Lava can be farmed by repeatedly mining and placing Hellstone in The Underworld.
- Placing gravity-affected Blocks such as Sand Blocks on top of Hellstone before mining will keep the Hellstone from inflicting damage.
- Hellstone, Meteorite, Luminite, and Obsidian are the only ores that do not have "ore" in the name.
- It is the only ore whose bar requires a material in addition to its ore.
- In the real world, silver nitrate is sometimes called "Hellstone".
- Hellstone has a special immunity to lava in the code, despite its rarity (Green) stopping that anyway.
- This is because before update 1.1, it had a rarity of White, so it needed that code to prevent it from burning.
- Desktop 1.2:
- Stack limit increased from 250 to 999.
- No longer causes invincibility frames when touched, instead giving the Burning Debuff.