43 C.F.R. § 3836.11

(a) Beginning in the assessment year that begins after you locate your mining claim, you must expend $100 in labor or improvements for each claim for each assessment year preceding the date on which you file for a small miner waiver.

(b) You may perform assessment work on:

(1) Each individual claim;

(2) One or more claims in a group of contiguous lode or placer claims that you own or hold an interest in and that cover the same mineral deposit; or

(3) Adjacent or nearby lands if the work supports development of the minerals on the claim(s).

(c) Your total expenditure must equal at least $100 per claim.