The stones you can pick-up from the ground aren't much use in construction other than for rubble-fill, which requires quantities vastly greater than available i

The stones you can pick-up from the ground aren't much use in construction other than for rubble-fill, which requires quantities vastly greater than available in free [position] material. To gather them in kilotonnes you'll need to remove and sift the regolith layer. A lot more expensive than 'pick some up'.