せきたん石炭sekitanいしずみ石炭ishizumi
1.
A combustible rock that resembles black stone, formed from ancient plant remains that accumulated underground and underwent decomposition and carbonization due to heat and pressure over geological time.
2.
A vital energy source classified into various types based on criteria such as heat value and the ratio of fixed carbon to volatile matter, often used as fuel or in chemical processes, and essential in the production of metallurgical coke.
3.
An organic material that has transformed through geological processes, typically characterized by its dark color and solid state, serving both as a fuel source and as a raw material in the coal chemistry industry.
Example:
石炭を石油の代わりに使いました。