siliceous tufa

例句：

1. 1. The rocks in the area are mostly composed of silica.
   该地区的岩石主要由二氧化硅组成。
2. 2.The fossilized tree trunk is a classic example of a siliceous rock formation.
   这种石化的树干是典型的硅质岩层形成的例子。
3. 3. The mineral deposits in this region are known for their siliceous composition.
   该地区的矿物矿床以其硅质成分而闻名。