Possible Clues:

• Treasure trove, figuratively
• Source of wealth, or type of bomb
• Source of wealth offered by Smith. Or just a claim to possession?
• Source of great riches
• Source of great wealth, or a potential danger
• Profitable venture
• Source of great profit
• Treasure trove yielding sudden wealth
• Soldier arrests elderly Frenchman with a fair amount of wine from lucrative venture
• Dig melon out -- get rich from this!