矸子 [－－]

Jyutping gon1 zi2
Pinyin gān zi

Definitions (CC-CEDICT)
  1. waste rock (mining)
  2. gangue (worthless minerals mixed in with coal or ore)
Definitions (Wiktionary)
  1. noun, colloquial
    coal gangue
    (syn.) 矸石, 死炭