stone slate

例句：

1. 1. The ancient city is surrounded by towering stone walls.
   这个古老的城市被高耸的石墙包围。
2. 2. Stones are used to build bridges and roads.
   石头用于建造桥梁和道路。
3. 3. The old castle was made of stone.
   这座古老的城堡是用石头建造的。