天河石

例句：

1. 1. The riverstone is a beautiful stone that has been used for centuries in traditional Chinese architecture.
   河石是一种美丽的石头，几千年来一直用于中国传统建筑。
2. 2. The riverstone was collected from the banks of the river and polished to a smooth finish.
   河石是从河流的岸边收集来的，经过打磨变得光滑。
3. 3. The riverstone was used as a decorative element in the ancient Chinese gardens.
   河石在古代中国园林中用作装饰元素。