- high-quality coal
(Can we date this quote?), Walter Hines Page, Arthur Wilson Page, The World's work, Volume 38:
- The drop in 1918 was also a fall in the production of black coal. In other words he losses were in the best coal, the gains in the poorer coal
- (nontechnical) coal
When used in comparison to brown coal or other grades of coal, the specific definition is likely intended. When used in comparison to white coal, or in a non-technical sense, it may mean any type of coal.
high quality coal