A permit, not including more than 2,560 acres (1,037 ha) in one State, is granted to prospect for chlorides, sulfates, carbonates, borates, silicates, or nitrates of sodium, and the royalty and rentals are similar to those for potash. Where necessary to secure the most economical mining, a person, association, or corporation may be permitted to hold up to 15,360 acres (6,221 ha) in one State.