Related Clues:

• 33rd st
• Contents of a vein pocket
• Source of slag
• Rock to be refined
• Subterranean resource
• It's found in lodes
• Prospector's target
• Rock for refining
• It's of miner interest?
• It may contain gold
• Motherlode yield
• Rock that's an asset
• Sphalerite, to zinc
• Rocky deposit
• Mine resource