This Dark Iron Ore farming guide will show you the best places for mining Dark Iron Ore. You can mine Dark Iron Ore with Mining skill 1, and you won't get ore fragments like with other ores.
However, smelting Dark Iron Ore requires Mining 230, and you also have to complete a quest in Blackrock Depths. Check out my Dark Iron Ore Smelting Guide if you want to learn how to smelt this ore.
Dark Iron Ore
Molten Core is the best place to farm Dark Iron Ore. One full clear gives you around 50-60 ores. It's a 40 man raid instance, so you can't farm here at lower levels. You should be around level 40 to easily pass every mob.
How to get to Molten Core?
You can find Molten Core inside Blackrock Mountain which is a zone in Eastern Kingdoms between the Burning Steppes and the Searing Gorge, linking the two regions, and you can enter from both zones. You'll have a partially open doorway, enter and follow the tunnel, when you come out you'll be in a large central chamber with lava in the bottom and a central rock chained to the sides.
Fly down to the location marked with X on the map. To enter the instance, you have to talk to Lothos Riftwaker, and he will teleport you to Molten Core.
Follow the route on the map below, mine every Dark Iron Deposit, and try to avoid pulling the bosses. It's crucial that you DON'T KILL ANY OF THE BOSSES, or this farming method won't work! If you accidentally pull a boss, try to run away as far as you can. Most bosses will reset if you pull them too far.
You can only do 10 instances in an hour, but mining every Dark Iron Deposit takes around 10 minutes, so you won't hit that cap. If you kill any of the bosses, this method won't work, you can't reset Molten Core once you killed a boss there.
A great (and only) alternative to Molten Core is Blackrock Depths. One clear takes around 6 minutes, and you will get around 15-20 Dark Iron Ore.
To get to Blackrock Depths, enter Blackrock Mountain from either southwest Searing Gorge or northwest Burning Steppes. After you enter Blackrock Mountain, open your map and head to the location I marked with a red X on the map below, then go inside the cave. Now you can open your map again, and you will see the entrance to Blackrock Depth on this map.
Once inside, follow the route below, but make sure to kill the Warbringer Construct in Hall of Crafting because they can drop Dark Iron Ore.
After killing the Warbringer Constructs follow the route until you reach the little drilling machine. Click on it and choose the option "Hit the button labeled as 'Entrance'". Hitting the button will teleport you to start of the instance.
Go outside, and you can reset the instance by right clicking over your portrait then click the "Reset all instance" button. This restarts the whole instance and all Dark Iron Deposit will be back. You can only do 10 instances in an hour, but mining every Dark Iron Deposit takes around 6 minutes, so you probably won't hit that cap unless you go too fast.