Related Clues:
- Ore locale
- Ore-rich vein
- Deposit of valuable ore found in surrounding rocks
- 66-Across source
- Rich deposit in a mine
- Copious source
- Fortunate miner's mother?
- Prospector's lucky strike
- Source, as of knowledge
- Substantial source
- The "mother" of deposits
- Hit the mother __ (strike it rich)
- Deposit of 17 Across
- Vein of mineral ore
- Mining vein