43 CFR §3837.11

1. (a)You may acquire a co-claimant's interest in a mining claim or site under the following circumstances:
   1. (1)You are a co-claimant who has performed the assessment work, made improvements, or paid the maintenance fees required under parts 3834 and 3836 of this chapter;
   2. (2)Your co-claimant fails to contribute a proportionate share of the assessment work, expenditures, or maintenance fees by the end of the assessment year concerned;
   3. (3)You notify the delinquent co-claimant of the alleged delinquency as provided in § 3837.21; and
   4. (4)If, within 90 days following the date the delinquent co-claimant received the notice provided for under § 3837.21 or 90 days following the end of the publication period described in § 3837.21, the delinquent co-claimant fails or refuses to contribute a proportionate share of the assessment work, expenditures, or maintenance fees, the remaining co-claimants acquire the delinquent co-claimant's share in the mining claim or site.
2. (b)You may not acquire a co-claimant's interest in a mining claim or site if the co-claimant is on active military duty.