Should any one apply to lease for prospecting and mining purposes the mineral deposits belonging to the state upon which improvements have been made, before the lease shall issue, to other than the owner of the improvements thereon, the applicant shall pay to the owner thereof the value of said improvements and shall file in the office of the state board of land commissioners a receipt showing that the price of said improvements, as agreed upon by the parties or fixed by appraisement under authority of the said board, has been paid to the owner thereof in full, or shall make satisfactory proof that he has tendered to such owner the price of said improvements so agreed upon or fixed by appraisement. The word "improvements" within the meaning of this section and of section 47-706 shall be construed to mean work performed in the development of the property, the estimated value of all known or probable mineral contained in the land that has been discovered or developed through mining excavations made by lessee, and all buildings, dwellings, mill machinery, mine machinery, trails, roads, and all equipment used, constructed and necessary for the operation of the mine, mill or plant.