In this section the following words have the meanings indicated. “Mine” includes a drift, shaft, slope, tunnel, underground room, and any other underground places or workings. “Mineral” includes clay, coal, and iron. An individual is a covered employee while working in or about a mine to extract minerals. An individual who is a covered employee under subsection (b) of this section is deemed to be employed entirely within this State if the mouth, principal entrance, or tipple of the mine in or about which the individual works is within this State, even if: a drift, shaft, slope, or other underground tunnel extends into an adjoining state; and the individual is injured or killed while working in the mine within the adjoining state.