Related Clues:

• Layers of rock
• They're mined and refined
• Smeltery material
• Refinery rocks
• Metal deposits
• They're mined, I tell ya!
• Smelters' raw materials
• Layers of rock, e.g.
• Iron sources
• Miner matters?
• Miners' quests
• Sources of metal
• Bauxite and borax, e.g.
• Metallurgists' supplies
• Lodes