Hard As Iron

Riddle: I can flow like a river, and come from dust, I age hard as iron, but never rust. What am I?

Answer: Concrete (liquid state before solidification).

Source: https://www.riddles.com/index.php/4528

I can flow like a river, and come from dust, I age hard as iron, but never rust. What am I? — Hard as Iron by George R v1.

Riddle: I can flow like a river, and come from dust, I age hard as iron, but never rust. What am I? Answer: Concrete (liquid state before solidification). — by George R v2.