Sandstone – Meaning, Uses, Facts, Properties & Color

Under the sea

Under the Land

The formation of sandstone occurs mostly into two phases, sedimentation/accumulation & compaction. Sedimentation of sand particles takes place either through water or air. Compaction occurs with physical pressure and chemical changes. The steps are:

1. Sedimentation of quartz crystals
2. Formation of cement & matrix
3. Formation of pores

• Clasts, also known as framework grains. Based on grain size, we can classify clasts into three categories: 
  • Fine-grains – 0.06-0.2mm
  • Mid-grains – 0.2-0.6mm
  • Coarse-grains – 0.6-2mm
• Based on the mineral compositions of the clasts, we can divide them into the following categories:
  • Quartz Grains, which predominantly contain quartz mineral with long survival capacity.
  • Feldspar Grains, which are found as either alkali or Plagioclase feldspar.
  • Lithic Grains, which are maybe from igneous, metamorphic, or sedimentary rocks. 
  • Accessory mineral includes micas, olivine, pyroxene, and corundum. These are forming a highly dense mass that renders sandstone a mature one.

• Cementing means binding. The cementing material in sandstone structure binds clastic framework grains or clusters of grains to gather firmly and becomes responsible for strength, durability, and wear & tears.
• Cement is the secondary material, which forms after sedimentation or deposition of grains.
• Based on the predominance of mineral types, we can classify cement in sandstone the following ways.
  • Siliceous Cement– It has silica or quartz particles that give the strongest bonds.
  • Calcareous Cement – It has calcites, and forms in patches leaving gaps open, so it makes sandstone porous.
  • Argillaceous Cement – It has clay particles, and forms softer types of sandstone.
  • Ferruginous Cement – It has ferrous content. So, it also is known as Hematite cement and gives reddish hues. 

• It is fine material.
• It founds within interstitial pore space among the framework grains of sandstone.
• Arenites sandstones contain very little amount of matrix, so those are clean type.
• Wackes are consisting of an abundance of the matrix, so those are dirty types of sandstone.

• Pores are open spaces within the rock mass. It gives porosity or permeability property to the sandstone rocks.
• Some sandstone types have tightly packed pores while some have loose binding between the clusters. 
• The occurrence of pores defines the porous nature of sandstone. 

General Properties:

• Variable colors and hues are found in sandstone. For instance, Beige, Black, Brown, Cream, Dark Brown, Green, Grey, Light Green, Light to Dark Grey, Pink, Red, White, Yellow, and some are Colorless.
• Darker hues of Sandstone indicates the presence of organic content like clay in the compositions. 
• Red, brown, yellow, and green colors are thanks to the presence of iron oxides in the clasts, cement, and matrix of Sandstone.
• It has clastic texture and visible only with a microscope.
• It is smooth to rough texture, mostly it is gritty to touch, so often hard to work. 
• It is sturdy, durable, and weather-resistant to apply in various construction applications, including interior and exterior.

Chemical Properties:

• Sandstone has various mineral content, such as Calcite, Clay, Clay Minerals, Feldspar, Micas, Quartz, and so on.
• The chemical compound content of Sandstone is Aluminum Oxide, CaO, Iron (III) Oxide, Potassium Oxide, MgO, Sodium Oxide, Silicon Dioxide, and so on.
• Biological, Chemical, & Mechanical Weathering are common in sandstone.
• Different types of erosions have exhibited in sandstone, including Chemical Erosion, Coastal Erosion, Glacier Erosion, Sea Erosion, Water Erosion, & Wind Erosion.

Physical Properties:

• It has a hardness of 6 to 7, and conchoidal fractures are present.
• It has coarse to fine grain size.
• Sandstone is a highly porous natural stone. 
• It has 95.00 N/mm2 compressive strength.
• It has 2.6 toughness and 2.2 to 2.8 specific gravity.
• The density of Sandstone is between 2.2 to 2.8 g/cm3 
• Its specific heat capacity is 0.92 kJ/Kg K, and it is heat, impact, and pressure resistant.
• It is slight water, scratch, wind, and acid-resistant, but not stain resistant. 
• Its appearance is rough thanks to high porosity, and it also makes it highly water and liquid permeable. Therefore, it is good in exterior applications in the construction. 

Sandstone Deposits:

• Its deposits found in Asian countries like China, India, Kazakhstan, Mongolia, Russia, Thailand, & Uzbekistan.
• In Africa, South Africa, Namibia, Nigeria, & South Africa.
• In Europe, Austria, Denmark, Germany, Great Britain, Netherlands, Norway, Poland, Sweden, Switzerland, & United Kingdom.
• In America, the USA, Canada, and Brazil.
• In Australia, New South Wales & New Zealand. 
• The formation of sandstone found mainly in the terrestrial milieu and marine milieu.

Terrestrial Environments (Both Land & Freshwater)

• •     Rivers (levees, point bars, channel sands)
  •     Alluvial fans
  •     Glacial outwash
  •     Lakes
  •     Deserts (dunes and ergs)

Marine Environments

• •     Deltas
  •     Beach and shoreface sands
  •     Tidal flats
  •     Offshore bars and sand waves
  •     Storm deposits (tempestites)
  •     Turbidities (submarine channels and fans)