Sedimentary Rocks After completing this section, students will identify sedimentary rocks and explain how they are formed (Standard PI – 024)

Sedimentary rocks are rocks that have been formed from pieces of other rock (sediments)

Sedimentary rocks are classified by three basic formation processes Clastic rocks Organic rocks Chemical rocks

Clastic Rocks – formed from fragments of other rocks Classified by particle size and shape

Conglomerate A cemented mix of rounded rock fragments

Breccia Cemented rock fragments with angular (sharp) edges

Sandstone – a cemented or compacted mix of sand-sized fragments Fragments of rock are about the size of the head of a pin and made mostly of quartz

Shale – compacted pieces of rock the size of flour particles Smooth, soft and easily broken

Chemical Rocks Formed when dissolved minerals precipitate out of lake, sea or underground water

Rock Salt It is typically formed by the evaporation of salty water

Rock Gypsum Gypsum rocks are sedimentary rocks made up of sulfate minerals

Limestone Limestone is produced from the mineral calcite (calcium carbonate) and sediment.

Organic Rocks Organic sedimentary rocks are composed of the remains of dead organisms.

Fossiliferous Limestone Limestone that contains large shell or coral fragments is called coquina.

Coal Coal forms from the build up and decay of plant and animal material that has been buried under layers of sediment