1. They invested their money in oil wells in Texas and they hit pay dirt. Now they’re the richest people I know.
2. Chuck went off to Alaska looking to hit pay dirt , but I don’t think he’s going to find what he wants. Everything worth finding has already been claimed.

Synonym: strike it rich. Compare to: hit the jackpot. The expression originates from the mining and gold-rush days when a person could become rich if he or she found dirt with gold in it.