yolk coal

例句：

1. 1. The yolk coal mine is located in the southwest of China.
   蛋黄煤矿位于中国西南部。
2. 2. The extraction process of yolk coal has become a hot topic in the industry.
   蛋黄煤的提取过程已成为该行业的热门话题。
3. 3. The yolk coal mine is a significant source of energy for the local economy.
   蛋黄煤矿是当地经济的重要能源来源。