Mining Hellstone can be a pain, not only because Hellstone deals fire damage to the player on contact (which can be negated with an Obsidian Skull, Obsidian Water Walking Boots, Lava Waders, Ankh Shield and Ankh Charm); but mainly because of the dangerous monsters of The Underworld, as well as the fact that Hellstone spawns lava (half a block per block of Hellstone ore) when mined.
One approach to mining Hellstone can be to just drop down to the Hellstone/Ash "floor" and start digging out the Hellstone. One must keep in mind, however, that Hellstone Bars are very expensive and difficult to acquire as 3 pieces of Hellstone and 1 piece of Obsidian are required to forge only one bar.
A second strategy is to build a little box around the hellstone with a low tier block, then simply mine inside of that box staying as close to the box as possible so that the mined hellstone will still gravitate towards the player.
A third method requires several Obsidian Skin Potions. You may also want to use a Cloud in a Bottle, Rocket/Spectre Boots, Flippers, or a Grappling Hook. Find a pool of lava, use the potions and jump in. They are usually large. Simply use the Grappling Hook to stick close to the Hellstone while mining, escaping when the potion supply runs out. This technique will collect a decent amount of Hellstone.
The fourth method is to dig all around the hellstone leaving one layer of any block between the player and the Hellstone. Then grapple onto the block and mine through it, picking the hellstone up.
Dealing with the Hellstone itself
As for dealing with the lava that is spawned when Hellstone is mined, you can use an Obsidian Skin Potion to negate damage from lava, as well as preparing a lava barrier to keep the lava from spilling onto you, and simply mine the Hellstone from behind the barrier. Prior to Update 1.1, you could also safely mine Hellstone by placing blocks of sand to soak up the lava formed as the Hellstone blocks broke. Another way is after mining, use a bucket and take the lava out.
Hellstone Bricks share a similar property, but do not produce lava when mined, instead only dealing contact damage.
- Hellstone will not spawn lava when mined if it is located outside of the Underworld. However, it will create lava if mined in Underworld even if it was placed down by player. This attribute means that lava can be farmed as long as you have at least a single block of Hellstone in the inventory.
- Unlike Bottomless Water Bucket, you cannot spawn lava anywhere, therefore Wired Pumps or Buckets are required.
- Due to a bug, Hellstone does not damage NPCs.
- Hellstone was added after a user suggested a "firestone" of sorts. 
- Despite the Guide claiming that Underworld is made of Hellstone, the majority of terrain were made by lava and ash blocks.
- Changed the recipe from 4 Hellstone and 1 Obsidian to 3 Hellstone and 1 Obsidian.
- Max stack increased from 250 to 999.
- Can be destroyed by explosions once the Wall of Flesh has been killed.
- Now gives off fiery sparks (Graphical effect only).
- Spawns lava when mined, but only when mined in the Underworld.
- Added to the game.
|Original Metals||Alternative Metals|
|Hard Mode Metals|
|Other Minerals & Materials|
|Items Requiring Hellstone|
|Tools||Molten Pickaxe · Molten Hamaxe|
|Weapons||Fiery Greatsword · Flamarang · Hellfire Arrow · Imp Staff · Molten Fury · Phoenix Blaster|
|Armor||Molten Helmet · Molten Breastplate · Molten Greaves|
|Potions||Flask of Fire|
|Other||Hellstone Bar · Hellstone Brick|