25 CFR §211.42

1. (a)Unless otherwise authorized by the Secretary, a lease for minerals other than oil, gas and geothermal resources shall provide for a yearly development expenditure of not less than $20 per acre. All such leases shall provide for a rental payment of not less than $2.00 for each acre or fraction of an acre payable on or before the first day of each lease year.
2. (b)Within twenty (20) days after the lease year, an itemized statement, in duplicate, of the expenditure for development under a lease for minerals other than oil and gas shall be filed with the superintendent or area director. The lessee must certify the statement under oath.