29 CFR § 570.53 - Coal-mine occupations (Order 3).
(a) Finding and declaration of fact. All occupations in or about any coal mine, except the occupation of slate or other refuse picking at a picking table or picking chute in a tipple or breaker and occupations requiring the performance of duties solely in offices or in repair or maintenance shops located in the surface part of any coal-mining plant, are particularly hazardous for the employment of minors between 16 and 18 years of age.
(b) Definitions. For the purpose of this section:
(1) The term coal shall mean any rank of coal including lignite, bituminous, and the anthracite coals.
(2) The term all occupations in or about any coal mine shall mean all types of work performed in any underground working, open-pit, or surface part of any coal-mining plant, that contribute to the extraction, grading, cleaning, or other handling of coal.