Limestone is a typical example of chemical rock. It is composed mostly of calcite. Some limestones are precipitated directly form sea or lake water. Others are composed largely of the shells of animals that lived in prehistoric seas.

• 石灰岩就是化学沉积岩中的一种典型代表，它主要由方解石矿物组成。有些石灰岩是由海水或湖水中物质直接沉淀而成，而另有一些石灰岩则大多是由生活在史前海洋中生物的外壳组成的，