Gravel is a very important construction aggregate.
Although it depends on the mechanics for how useful 2 would be. Does the gravel just like appear near you? Is there just a guy who gives you bags of gravel? Do you have to go to a specific location to get it? Is there a limit to the through put? What’s the volume of output of the gravel. what type of gravel is it? Could it be processed for other minerals?
Like, free gravel sounds pretty damn awesome based on the mechanics.