Water weighs 8.34 pounds per gallon and there are 7.48 gallons per cubic foot, therefore water weighs 62.4 pounds per cubic foot at normal temperatures (~60 - 80 degrees F).
An individual rock (or other mineral matter) has a density greater than that of water, however, it’s bulk density will be less because of void volume.
If the previously stated number of one ton per cubic yard then concrete would weight ~ 74.7 pounds per cubic foot which is too low.
I checked it out and here’s a link to site where the value is given as 135 - 142 pounds per cubic foot depending on the admixture and aggregates used.
Weight of a Cubic Foot of Concrete