US Department of Labor

“ Mining operations are classified, by industry, on the basis of the principal mineral produced, or, if there is no production, on the basis of the principal mineral for which exploration or development work is in process. The mining of culm banks, ore dumps, and tailing piles is classified as mining according to the principal mineral product derived. ”

“ Mining This division includes all establishments primarily engaged in mining. The term mining is used in the broad sense to include the extraction of minerals occurring naturally: solids, such as coal and ores ”