Ground Netherrack
Crafting
Ground Netherrack is created by placing Netherrack in a mechanically powered Mill Stone.
Applications
Ground Netherrack is used to make Soul Urns and Hellfire Dust. To do so you need to pass Ground Netherrack over a Hopper with Soul Sand in the filter slot, an Urn placed directly underneath it, and is receiving mechanical power. After passing over the Hopper the Ground Netherrack will separate into Hellfire Dust and souls. After filtering 8 Ground Netherrack into Hellfire Dust, the souls will be trapped in the Urn and make a Soul Urn
Keep in mind
You can make Hellfire Dust without Urns but you need to power the Hopper or... well lets just say that you really want to power that Hopper. Necromantic energy overload isn't a pretty thing.