(a) Lessee shall furnish with each mining lease a bond (Form 5-154b), and an assignee of a lease shall furnish with each assignment a bond (Form 5-154m), with an acceptable company authorized to act as sole surety, or with two or more personal sureties and a deposit as collateral security of any public-debt obligations of the United States guaranteed as to principal and interest by the United States, equal to the full amount of such bonds, or other collateral satisfactory to the Secretary of the Interior, or show ownership of unencumbered real estate of the value equal to twice the amount of the bonds. Lessee may file a bond on Form 5-154a without sureties and a deposit as collateral security of Government bonds equal in value to the full amount of the bond. Lease bonds, except as provided in paragraph (c) of this section, shall not be less than the following amounts: For less than 80 acres$l,000
For 80 acres and less than 120 acres1,500
For 120 acres and not more than 160 acres2,000
For each additional 40 acres, or part thereof, above 160 acres500
Provided, That for leases for minerals other than oil and gas the Secretary of the Interior or his authorized representative with the consent of the Indian landowner may authorize a bond for a lesser amount if, in his opinion, the circumstances warrant and the interests of the Indian landowners are fully protected: Provided further, That a lessee may file a bond (Form 5-154f), in the sum of $15,000 for all leases of minerals up to 10,240 acres under the jurisdiction of the officer in charge of the Five Civilized Tribe Agency.