Related Clues:

• Kind of deposit
• Cinnabar, for one
• Prospector's prize
• Blast furnace input
• Igneous rock source
• Assayer's subject
• Sourdough's strike
• Specimen for an assayer
• Find for 8-Across
• Silver or iron, e.g.
• Deposit in some banks
• Miners dig it
• Rockhound's find
• Nickel in a pocket, perhaps?
• Quarry product