IPA: /ˈkoʊlfeɪs/
KK: /ˈkoʊlfeɪs/
The area in a mine where coal is being extracted or the visible surface of coal.
The miners worked hard at the coalface to extract the valuable resource.
Coalface is formed from "coal" (from Old English "cal", meaning a black combustible mineral) and "face" (from Old French "face", meaning the front or surface of something). The term "coalface" refers to the exposed surface of a coal seam in a mine, where coal is being extracted.
Think of the 'front' or 'surface' ('face') of the 'black mineral' ('coal') that miners work on — that's what coalface means.