Originally posted by TheBoot:

Hmm... Sounds similar to Surtling Core. What are they used for? Bon Fires, Smelter, Kiln, Blast Furnace, Portals. Would be cool if you could construct a new Portal with them that allowed you to transport ores and ingots but I doubt that. Devs haven't indicated any flexibility in that area. I would assume it's used in a new crafting device. Maybe it's required for that new Forge they showed awhile back? Maybe it's needed to build a marble cutter for the new black marble material?

Those all sound like good guesses to me!
I really want a Muspell Maul with huge fiery AoE. :D