noun, noun which may take the genitive case particle 'no'
lignite; brown coal
A type of low-grade coal; used in geological, industrial, or energy contexts.
亜炭は石炭の中でも炭化度が低い。
Lignite has a low degree of coalification among coals.
この地域では亜炭が採掘されていた。
Lignite was mined in this region.