alum shale

例句：

1. 1. The oil field is richin alum shale, which isvery important for oil extraction.
   这个油田富含铝石，对石油开采非常重要。
2. 2. Alum shale is a type of sedimentary rock that contains a lot of aluminumminerals.
   铝石是一种含有丰富铝矿物的沉积岩。
3. 3. The alum shaleformation is an important source of aluminum andother metals.
   铝石层是重要的铝和其他金属来源。