Related Clues:

• See 63-Across
• It may be picked
• Miner's quarry
• Source of iron
• It may have a silver lining
• Tram filler
• It's hot stuff
• It's fine for a refinery
• Pay dirt
• Miner's quest
• Lead ___
• Bauxite, e.g.
• Subject of testing
• Zoomed
• Hematite, for one