hard zone crack

例句：

1. 1.The rock is so hard that it's difficult to drill a hole in it.
   这块岩石太硬了，很难在它上面钻孔。
2. 2. The hard zone cracks are visible on the surface of the rock.
   岩石表面的硬区裂缝是可见的。
3. 3.The engineer carefully studied the hard zone cracks in the area before making any decisions.
   工程师在做出任何决定之前，仔细研究了该地区的硬区裂缝。