A mill site is a location of nonmineral land not contiguous to a vein or lode that you can use for activities reasonably incident to mineral development on, or production from, the unpatented or patented lode or placer claim with which it is associated.

(a) A dependent mill site is used for activities that support a particular patented or unpatented lode or placer mining claim or group of mining claims.

(b) An independent or custom mill site—

(1) Is not dependent on a particular mining claim but provides milling or reduction processing for nearby lode mines or a lode mining district;

(2) Is used to mill, process, and reduce either—

(i) Ores for other miners on a contractual basis; or

(ii) Ores that are purchased by the independent or custom mill site owner.

(3) You may not have a custom or independent mill site for processing materials from placer mining claims.

The maximum size of an individual mill site is 5 acres. You may locate more than one mill site per mining claim if you use each site for at least one of the purposes described in § 3832.34 of this part. You may locate only that amount of mill site acreage that is reasonably necessary to be used or occupied for efficient and reasonably compact mining or milling operations.

(a) You may locate a mill site in the same manner as a lode or placer mining claim, except that—

(1) It must be on land that is not mineral-in-character; and

(2) You must use or occupy each two and a half acre portion of a mill site in order for that portion of the mill site to be valid.

(b) If the United States does not own the surface estate of a particular parcel of land, you may not locate a mill site on that land under the General Mining Law or the Stockraising Homestead Act (see part 3838 of this chapter).

(a) Upon obtaining authorization under the surface management regulations of the surface managing agency, you may use and occupy dependent mill sites for:

(1) Placement of grinding, crushing, or milling facilities (such as rod and ball mills, cone crushers, and floatation cells) and reduction facilities (such as smelting, electro-winning, roasters, autoclaves, and leachate recovery);

(2) Mine administrative and support buildings, warehouses and maintenance buildings, electrical plants and substations;

(3) Tailings ponds and leach pads;

(4) Rock and soil dumps;

(5) Water and process treatment plants; and

(6) Any other use that is reasonably incident to mine development and operation, except for uses exclusively supporting reclamation or mine closure.

(b) Upon obtaining authorization under the surface management regulations of the surface managing agency, you may use and occupy independent mill sites for processing metallic minerals from lode claims using:

(1) Quartz or stamp mills; or

(2) Reduction works, including placement of grinding, crushing, or milling facilities (such as rod and ball mills, cone crushers, and floatation cells), reduction facilities (such as smelting, electro-winning, roasters, autoclaves, and leachate recovery), tailings ponds, and leach pads.