Sentence:  The Secretary of the Interior or any duly authorized representative shall be entitled to admission to , and to require reports from the operator of , any metal or nonmetallic mine which is in a State ( excluding any coal or lignite mine ) , the products of which regularly enter commerce or the operations of which substantially affect commerce , for the purpose of gathering data and information <WSD>necessary</WSD> for the study authorized in the first section of this Act . 
Meaning of the word marked with <WSD> tags:  absolutely essential