Sandstone is a sedimentary rock that is made up mostly of tiny grains of quartz. Most sandstone is formed in oceans, lakes and rivers where tiny bits of rock and dirt settle to the bottom. After thousands of years, these layers of sand get buried under tons of more sand and dirt until it is turned into solid rock. Sandstone can be found in many colors like those you can see in the picture and has a texture that feels like sandpaper.