Related Clues:

• Magnesium source
• Miner's discovery, perhaps
• It needs refining
• Lignite or anthracite
• Klondike find, perhaps
• Mineral bearing rock
• Get a lode of it
• Underground treasure
• Snowman's eyes
• It's found in seams
• Galena, for instance
• Furnace fodder, perhaps
• It needs refinement
• Furnace fuel, sometimes
• Lignite, for one