Related Clues:

• Blast furnace input
• Assayer's subject
• Sourdough's strike
• Specimen for an assayer
• Find for 8-Across
• Scuttle filler
• Silver or iron, e.g.
• Energy source
• Deposit in some banks
• Miners dig it
• Rockhound's find
• Nickel in a pocket, perhaps?
• Quarry product
• Miner's load
• Vein filler