colliery screened 中文意思是什麼

colliery screened 解釋
採煤場篩選過的煤精選的煤
  1. To this day coal is said to be screened in the colliery when it has stone and other impurities removed from it.

    據說煤中摻有石子和其它雜質須去掉時,至今仍得把煤在礦上篩過。
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