hard clay

例句：

1. 1. The hard clay is difficult to work with and requires a lot of water.
   这种硬粘土很难加工，需要大量的水。
2. 2. The farmer used the hard clay to make bricks for his house.
   这位农民用这种硬粘土来制作砖块建造他的房屋。
3. 3. The hard clay was used in ancient times as a building material.
   古代人们使用这种硬粘土作为建筑材料。