Sixth Grade
Worksheets
Non-Clastic Sedimentary Rocks
Rocks can be put into three main groups. They are grouped by how the rocks formed. Sedimentary (sed-uh-MEN-tuh-ree) rocks are formed on or near Earth's surface. Sedimentary rocks are sorted into other groups. They can be sorted as clastic or non-clastic. This group tells something about the rocks' beginning and what they formed from.
Non-clastic rocks are created when water evaporates or from the remains of plants and animals. Limestone is a non-clastic sedimentary rock. Limestone is a common building material. Limestone is made of the mineral calcite. It often contains fossils. Limestone formed in the ocean from the shells and skeletons of dead sea creatures. Some of the fossils in limestone are too small to be seen without a microscope. Chalk is a type of limestone that is usually white. It consists almost entirely of the shells of tiny dead sea creatures.
Coal is another non-clastic rock. It formed from the dead remains of plants. Millions of years ago, plants fell into swamps. They were covered with layers of sediment and did not rot. Over millions of years, as the remains were buried deeper under more and more layers of sediment, they were changed by pressure into coal. Coal is commonly used as fuel in power plants to make electricity.
