Sand

• All sandstone contains sand, defined as small grains ranging from 0.0025 to 0.08 inch, or 0.063 to 2 mm. Sand is very porous with water flowing straight through it. When sand transforms into sandstone it retains some of that porous characteristic. This makes sandstone valuable for holding water in what is called a sandstone aquifer. Principal sandstone aquifers in the United States found at or near the surface are primarily located in the upper Midwest, Rocky Mountain states and in western Pennsylvania, eastern Ohio and West Virginia, according to a map by the U.S. Geological Survey.
  
  

Texture

• The texture of sandstone depends upon the circumstances surrounding its formation. Geologists study the size and shape of the grains of sand looking for clues as to its origin. For example, the lack of any fine grains of sand indicates the sandstone was formed by such action as waves striking a beach, wind on sand dunes or a strong river current. Shape is also important; the roundness of the grain indicates how far the grain traveled before forming the sandstone.
  
  

Mixture

• The mixture of sand and the other materials impacts the texture of sandstone. Sandstone formed recently tends to have a higher composition of sand while ancient sandstone may have more of the binding materials. The ratio of sand to binding materials determines not only how porous the sandstone is, but its texture. Quartz, or silica, when combined with sand produces a vary hard sandstone. The opposite effect occurs with clay and gypsum; the sandstone is soft and the sand may come off in your hands when holding the sandstone.
  
  

Classification

• Sedimentary rocks are classified according to their texture and composition. An example is the arkose sandstone which is a rock with a high percentage of feldspar, according to an article about classification by James Madison University. The article lists the four classifications: quartz, feldspar, lithics and matrix. Lithics is a catchall for any rock that is not quartz and feldspar, while matrix is a mixture, such as silt and clay found in sandstone.