- Look, it's all over here. I think we've found a... What do you call it?
- A mother lode.

4 seconds sound clip from the The Treasure of the Sierra Madre movie soundboard.

You can hear this line at 00:27:45.441 in the Blu-ray version of the movie.

Quote context

[...]

- Hey.

- What's the matter?

- Look. Look at it glitter. It's yellow, too, like... like... gold.

- Howard! Howard! Howard! Howard! Come back! We've found something!

- Hey, look! Hey, look, Curt! There's a vein of it here in this rock. And look here!

- Look, it's all around. I don't know what else could it be. Only gold shines and glitters like that. We've struck it, Curt.

- Look. From the looks of things, we've struck it rich.

- Look, it's all over here. I think we've found a... What do you call it?

- A mother lode.

- Howard! Howard! Come on, look! Look! Here!

- Look at this rock. It's full of gold! Veins of it.

- That wouldn't pay your dinner for a carload.

- It ain't gold?

- Pyrites. Fool's gold.

- Oh, not that there ain't plenty of the real stuff hereabouts. We've walked over it 4 or 5 times.

- That place yesterday looked like rich diggings, but the water for washing the sand was 11 miles away... too far. And the other places... well, there wasn't enough gold to pay us a good day's wages.

[...]