Subbituminous coal - Alexeitan

Japanese: 亜歴青炭 - アレキセイタン

When coal in the broad sense is divided into four stages according to its degree of coalification (anthracite, bituminous coal, subbituminous coal, lignite), the coal with the second lowest degree of coalification after lignite is called subbituminous coal. When coal in the broad sense is divided into two major stages according to its degree of coalification, coal (narrow sense) and lignite (broad sense), it is included in the broad sense of lignite. The coal quality of the Kushiro coalfield and Joban coalfield falls into the range of subbituminous coal, but in Japan these are also called coal. The term subbituminous coal is used exclusively to refer to imported coal. The major sources of subbituminous coal are the United States and Russia, and much of it is from the Jurassic and Cretaceous periods of the Mesozoic era.

Source: Heibonsha World Encyclopedia, 2nd Edition Information

Japanese:

広義の石炭を石炭化度によって4段階(無煙炭，歴青炭，亜歴青炭，褐炭)に区分するとき，石炭化度が褐炭に次いで低いものを亜歴青炭という。広義の石炭を石炭化度によって石炭(狭義)と褐炭(広義)に二大別したときは，広義の褐炭に含まれる。釧路炭田･常磐炭田の炭質は亜歴青炭の範囲に入るが，日本ではこれらも石炭と呼ばれている。亜歴青炭の語が用いられるのは，もっぱら外国炭についてである。亜歴青炭の大資源国はアメリカとロシアで，地質年代としては中生代ジュラ紀と白亜紀のものが多い。

出典　株式会社平凡社世界大百科事典第２版について　情報

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