In placer and hydraulic mining, sand or gravel containing, or supposed to contain, gold enough to pay for washing. Also wash-stuff, wash-gravel.(noun)
The Century Dictionary (Public Domain)
Use "wash-dirt" in a sentence
"Every man that had a few pounds wanted a horse to ride or drive; every miner wanted a wash-dirt cart and a horse to draw it."
"If they found the colour of gold, the least trace of it in a dish of wash-dirt, they would at once settle down themselves."
"All being made ready, and every possible precaution taken against accident, I was let down from the top of the cliff to what looked like the dried-up course of a stream composed of pebbles and wash-dirt."