It’s All About the Sediment

To recognize a sedimentary rock, you must look at the sediment that makes up the rock. Some sedimentary rocks have small grains, such as silt or sand, in them. You can see a grainy texture if you look closely. Other sedimentary rocks have crystals in them. The crystals may be small or fairly large.

Grainy sedimentary rocks are given names based on the size of their grains. Sandstone is made of grains of sand. Conglomerate has a mix of sand and gravel. Shale has grains of silt or clay in it.

Sedimentary rocks with crystals often sparkle. Some limestones twinkle in the light. Rock salt is another example. It is a light-colored rock made from crystals of salt.

This chart can help you identify different kinds of sedimentary rocks.View Larger Image

(conglomerate) © www.iStockphoto.com/Joe Potato; (limestone) © www.iStockphoto.com/Justin McDonald; all other images Shutterstock.com