mother of coal

短语

释义与例句

n.
  1. 1.

    Synonym of fusain (“fossilized charcoal”).

    不可数 商务 采矿

词源

Apparently named via an instance of the same theme whence also mother of pearl and mother of vinegar: a matrix that produces (or was believed to produce) the end product and also coexists therewith.

来源：wiktionary