Nothing in sections
75 of this title shall be construed to destroy or impair any rights which may have attached prior to the third day of March, 1873, or to authorize the sale of lands valuable for mines of gold, silver, or copper.
(R.S. § 2352.)
R.S. § 2352 derived from act Mar. 3, 1873, ch. 279, § 6,17 Stat. 608.