Most of the people who became wealthy during the gold rush did not strike it rich panning in the gold fields. They got rich by "mining the miners."

What does the term "mining the miners" refer to?

Collecting gold from the hair and clothes of miners arriving from the diggin's.

Re-panning an area that other miners had already mined.

Getting the hard-earned gold from a miner by selling them food and necessities at exorbitant prices.