The Mining Law, as amended, opened the public lands of the United States to mineral acquisition by the location and maintenance of mining claims. Mineral deposits subject to acquisition in this manner are generally referred to as "locatable minerals." Locatable minerals include both metallic minerals (gold, silver, lead, copper, zinc, nickel, etc.) and nonmetallic minerals (fluorspar, mica, certain limestones and gypsum, tantalum, heavy minerals in placer form, and gemstones). It is very difficult to prepare a complete list of locatable minerals because the history of the law has resulted in a definition of minerals that includes economics.
Starting in 1873, the Department of the Interior began defining locatable minerals as those minerals thatare:
- recognized as a mineral by the standard experts,
- are not subject to disposal under some other law, and
- make the land more valuable for mining than for farming.
Minerals normally locatable on lands acquired (purchased or received) under the Acquired Lands Act of 1947 by the United States or found on Indian reservations are subject to lease only (43 CFR Group 3500).
Since 1955, common varieties of sand, gravel, stone, pumice, pumicite and cinders were removed from the Mining Law and placed under the Materials Act of 1947, as amended. Use of salable minerals requires either a sales contract or a free-use permit. (43 CFR Part 3600).
Uncommon varieties of saleable-type minerals may be locatable if the deposits meet certain tests created by various judicial and administrative decisions. Federal certified mineral examiners determine uncommon variety minerals on a case-by-case basis.(43 CFR Part 3830, Subpart C)
Since 1920, the Federal government has leased fuels and certain other minerals, charging a royalty on the value of the mined and sold material. Today, minerals that are subject to lease include oil and gas, oil shale, geothermal resources, potash, sodium, native asphalt, solid and semisolid bitumen, bituminous rock, phosphate, and coal. In some states, sulphur is also subject to lease.
