What Type of Rock is Sandstone
Sandstone is a type of sedimentary rock. It is considered to be clastic, meaning it is made up of preexisting rocks and minerals such as sand particles. Sandstone can also be made up of larger clasts and fragments that overtime have been cemented together.
Sandstone is primarily made up of quartz and to a lesser degree feldspar due to their abundance on the earth. To what degree that those small rocks, minerals, and sometimes organic material which form sandstone, will be entirely up to the source where they came from.
Sandstone is formed by weathering rock being broken down into grain sized particles of sand and rock. These grains are then transported by air, water, or even ice and deposited as sediment to a resting location where sandstone can continue its formation.
In the Geology world, particles of sand or small rocks are looked at in what’s known as grain size. The size of these grains of rock are in the range of 0.0625mm to 2mm. By definition, grains in this size range are what will generally be called sandstone.
All those particles of sand and rock don’t just stick together on their own. Additional material such as clay, calcite, silica, or even silt, just to name a few, will act as a bonding agent to seal all those grains together. With the added pressure from layers after compacted layers, the final result will give you sandstone.
The Uses of Sandstone
Sandstone uses will be in regards to cosmetic appeal for homes, buildings, parks, and gardens. Some additional regular uses of sandstone may include; pathways, benches, walls, statues, and other types of sandstone constructions.
Sandstone is notably easy to carve and work with. Some sandstone’s are a bit too soft for building purposes and can show signs of wear over time depending on its use. Other forms of sandstone can be fairly tough, and even contain some fairly strong sediment contents so as to create grindstones for sharpening metal blades and even grindstones for mincing grain.
Other uses can be in the creation of jewelry, boxes, candle holders, vases, tile, fireplaces, pillars, tables, garden balls, shelves, coasters, stepping stones and of course you can just have some display pieces to show off to your friends and neighbors.
There are many uses for sandstone which all cannot be named. Outside of cosmetic appeal, sand and sandstone are noted for containing most of the world’s oil and natural gas. Sandstone having a very porous nature, can hold vast amounts of liquid within it. Sandstone is one of earths ways of holding water in what is known as aquifers. This water can move through the ground and come out onto the surface as springs. Many will create wells and pumps to tap into these aquifers to bring its water to the surface. There are many known aquifer locations around the world.
The Colors of Sandstone
Sandstone color can range from white, black, grey, tan, brown, oranges, yellows, pink, and reds. These colors are often due to the elements contained within the sandstone known as its mineralogy and how the weathering of all those grains within the sandstone happened.
Sandstone at times can look like any other type of rock. What sets this rock apart from the others can be the notable colors and patterns.
Sandstone can look like it has streaks or banding in one direction where the colors can vary from darker to lighter. Iron oxide present in sandstone will contribute to the reddish hues of color you might see in some sandstone. The colors of the quartz or feldspar sand particles will generally make up the color of the sandstone itself.
What is Sandstone Worth
The worth and value of sandstone can all depend on its form. If you are paying for sandstone tiles or pathways expect to pay $25 to $60 per square foot. As soon as you start carving in sandstone, you can expect pay under $100 for a nice figurine or statue depending on size.
Not all sandstone is equal though. Some sandstone is more sought after due to its patterns and colors. Navajo Sandstone sculptures are quite beautiful and will fetch some much higher prices.
For the most part, sandstone is very affordable and you will quite often find it being displayed in many locations throughout the world.
7 Diagenetic Sandstone Formation Process
The process of forming sandstone can be fairly detailed. There are 7 diagenetic processes, physical and chemical changes, which will convert sediment into sedimentary rock. I will briefly describe each:
| Compaction | This is the stage at which layer after layer of sediment results in previous layers becoming more compact. This creates great pressure on earlier layers. |
| Recrystallization | With the greater amounts of pressure and even temperature, minerals within the sediment will dissolve and reform. |
| Solution | This is the dissolving of minerals by passing of fluid through the sediment. These dissolved minerals can be transported out or into other sediment. |
| Cementation | This is the process of minerals locating into pore spaces to create a cement hold for the grains of rock or sand. The most common cement material is Calcite. Other cement minerals are quartz, hematite, clay minerals, anhydrite, barite, feldspar, gypsum, and zeolite. |
| Authigenesis | This is when new minerals are introduced by means of fluid to the sediment and crystalized. This can be from actual new minerals introduced or chemical reactions forming new minerals. |
| Replacement | This is when existing minerals are replaced by new minerals. Some notable occurrences of a replacement phase include: opal, quartz, and dolomite. |
| Bioturbation | This is the process by which biological life will move around in the earth (e.g. small animals and worms) and will further compact sediment. Their mineral rich excrements will be the cement bonding agent. |
One thing most people don’t think of when it comes to sandstone is that it can contain organic material within all those grains of sand and small rock. Imagine years of time going by in a large body of water where not only particles of sand and rock accumulate at the bottom, but also plant life, fecal matter, and the very remains of the water creatures themselves.
Sandstone Fossils
One of the most wonderful phenomenon in the rock and mineral world is the capturing of fossils within sedimentary rock. Fish fossils, snails, corrals, clams, and other life can be trapped in sedimentary rock such as sandstone.
Some sandstone’s will contain fossils, but typically most fossils are found in limestone. This is due to the nature of some sandstone’s being too porous and allowing organic matter to dissolve or easily decay. At times the very environment will simply not allow formation of fossils in sandstone.
In some locations when animals and plant life die, they will settle to the bottom of a body of water. Grains of small rock and sand along with the addition of smaller grained mud, will cover these organisms and create a seal. This seal will leave little air or outside exposure for its organic contents.
The lack of earthly elements getting to the organic life trapped inside the sediment, undoubtedly helped preserve their remains. As layer upon layer form in this manner, pressure and heat from the earth will produce a sold form of rock with these trapped fossils.
It should also be noted that seismic events that occurred such as volcano’s, mudslides, and earthquakes contributed to the destruction of larger groups of animals and plant life. These animals and plant life could then be covered, preserved, and captured in sedimentary fashion in that reckonable time event.
Notable Places to View Sandstone Formations
Acacus/Tadrart Mountains Sahara Desert, Libya
Purnululu National Park, Australia
Arches National Park, Utah, USA
