It depends on whether the collecting activity is commercial or noncommercial in nature and subject to river-administering agency regulation. Mining under the 1872 mining law is a commercial and business activity tied to valid existing rights of claims and is regulated as such (36 CFR 228, 43 CFR 3809, 8365, et al).
Non-commercial mineral collecting for recreational purposes (e.g., hobby collecting, rock-hounding, gold panning, sluicing, or dredging) may be authorized by the Bureau of Land Management or the U.S. Forest Service depending on the amounts collected, size and scale of...