Mudstone – Meaning, Uses, Facts, Properties & Color

Mudstone – Meaning, Uses, Facts, Properties & Color

Mar 27, 2023

What is Mudstone?

Mudstone is a kind of Murdock chiefly contains mud or clay in its composition. It is a fine-grained sedimentary rock with a grain size of 0.063mm. Thus, minute grain size renders it impermeable for water or any liquid to pass through and leave useless for the construction industry in the direct applications.


Formation of Mudstone

When very fine-grained clay particles are depositing in water and overtime buried and compacted thanks to the sedimentation process turn into mudstone.

Types of Mudrock

Mudrock is a parent class, and mudstone is a category. Siltstone, Claystone, and mudstone are three categories of mudrock, and shale and argillite are sub-categories of mudstone.

Let’s see the differences and characteristics of each category and sub-category falls into Mudrock.


  • Grain Size (in µm) – Min. 4 to Max. 64
  • It contains more than 50% of silts-sized particles.
  • It is lithified & non-fissile mudrock.
  • It is 1/16 of a millimeter in particle size.
  • Himalaya in India is the biggest reservoir of silt in the world.


  • Grain Size (in µm) – Min. 0 to Max. 4
  • It is 1/125 of a millimeter in particle size.
  • It constitutes more than 50% of clay-sized particles.
  • It also is lithified & non-fissile mudrock.
  • More than 35 clay minerals species recognized on the Earth, and these clay minerals are integrated into Claystone affect different properties like cohesive, plastic, and flow.
  • Quartz, iron oxides, feldspar, and carbonates are often part of the Claystone.
  • Soil, volcanic ash, and glaciation are principal sources of clay, and feldspar, amphibole, volcanic glass, and pyroxenes are other donors of the clay for the formation of Claystone.


  • Grain Size (in µm) – Min. 0 to Max. 64
  • It has a mix of clay-sized & silt-sized particles.
  • It is a silicic-clastic sedimentary rock.
  • It is found in every region of the world and under the earth crust where natural gas and oil reservoirs are found. In fact, Mudrock is prime cause to form those reservoirs.

Shale and Argillite are sub-categories of mudstone.


  • Grain Size (in µm) – Min. 0 to Max. 64
  • It shows fissility or lamination
  • Laminated-made of thin layers.
  • Fissile-cleavage occurs parallel to lamination layers into thin slices.
  • It has a wide range of colors, including red, brown, green, gray, and black.
  • Shale is an excellent material to produce clay mainly used in the formation of bricks, tiles, pipes, and pottery.
  • Shale has oil & gas content in deep layers of the earth, and recent horizontal drilling has made it possible to extract non-conventional resources using Hydraulic Fracturing techniques.
  • Feldspar, quartz, and chert are predominant content in Shale along with minerals and organic compound usually found in other Mudstone varieties.
  • Shale also found on the Mars planet.


  • Grain Size (in µm) – Min. 0 to Max. 64
  • It has undergone low-grade metamorphism.
  • The formation of Argillite takes place from the lithified muds and oozes.
  • Argillite predominantly composed of indurated clay particles in silt sizes.
  • It is high in aluminum and silica with alkali and cat-ions of alkali.


  • It is a fine-grained homogenous rock.
  • The formation of Slates takes place from clay (Mud) and volcanic Ash. So, it is a kind of Mudrock in true sense.
  • The formation takes place through low-grade metamorphism and resulting in foliated rocks. The foliation is known as Slate Cleavage in the industry.
  • If careful cut made by experts, slate also display Fissility property found in Mudrock. The cut must be striking parallel to the foliation so that it can yield Shale like stone pieces useful in various construction works.
  • Argillite predominantly composed of quartz and illite
  • It is a great material for roof tiles and the creation of paths and patios for exterior applications.

Properties of Mudstone

Professionals in the stone industry and allied engineering are often interested in some basic yet scientific facts before deciding the usage of natural stones. Physical, chemical, and other application-specific info become vital for them. Thereby, I have listed some important properties of Mudstone here.

General Properties

  • Mudstone is available in different colors, including Black, Blue, Brown, Green, Grey, Orange, Red, White, Yellow, and in different hues of black color.
  • Gray to black hues of mudstone indicates the presence of organic content (including natural oil & gas) in more than 1% of compositions.
  • Red, brown, yellow, and green colors are thanks to the presence of iron oxides in the sediments of mudstone.
  • It has clastic texture and visible only with a microscope.
  • It is smooth to touch and too soft to work.
  • It has three types: Marl, Shale, and Argillite.

Chemical Properties

  • Mudstone contains different mineral content, such as Feldspar, Micas, Pyrite, Quartz Biotite, Chlorite, Plagioclase, Muscovite or Illites, and so on.
  • The chemical compound content of mudstone is Aluminium Oxide, NaCl, CaO, Iron (III) Oxide, Silicon Dioxide, and so on.
  • Mudstone has three kinds of clay minerals, including KaolinitesSmectites, and Illites. Kaolinites formed only in a humid climate. Smectites are expanding types, and Illites formation takes place due to weathering.
  • The impacts of chemical and mechanical weathering are obvious on mudstone.
  • Similarly, different erosions like chemical and water (sea or river) also are apparent.

Physical Properties:

  • Its hardness scale ranging between 2 to 3 and fractures are absent.
  • It has 2.6 toughness and 2.2 to 2.8 specific gravity.
  • The density of mudstone is between 2.4 to 2.8 g/cm3
  • Its specific heat capacity is 0.39 kJ/Kg K, and it is heat as well as impact resistant.
  • It is slight water resistance, but not scratch, stain, wind, and acid-resistant.

Mudstone Deposits:

  • Its deposits found in Asian countries like India, China, Bangladesh, and Russia.
  • In Africa, South Africa, Ethiopia, Kenya, Morocco, and Tanzania.
  • In Europe, France, Germany, Greece, Italy, Romania, Austria, Scotland, Spain, and Switzerland.
  • In America, USA, Bolivia, Chile, Colombia, Ecuador, Peru, and Venezuela.
  • In Australia, New South Wales, New Zealand, Queensland, Victoria, and Western Australia.
  • The formation of mudrock takes place in reducing conditions in clam or stagnant water found in
    • Alluvial environment
    • Glaciers and non-glacial lakes
    • Deltas
    • Coastline
    • Marine environment
    • Freshwater environment

Uses of Mudstone

Mudstone, like other natural rocks, has usages in constructions of exterior and interior application. Besides these, it has some industrial/commercial applications worth to know.

Interior Applications

The softness and flexibility of mudstone make it useful elements for decoration rather than load-bearing applications in buildings.

Mudstone as Decorative Aggregates

Mudstone pebbles are excellent material to do a stone painting for various decoration purposes including on various religious and cultural occasions.

Mudstone as Entryway Stone

Soft and brittle mudstone has extreme decorative properties, and creating a cool welcoming gesture on the entryway is the traditional application of mudstone here.

Mudstone as Flooring Stones

Many regions have the availability of local mudstone inventory in a range of strength and colors. Gray to dark black colors is common in the mudstone category of natural stones. Appropriate polishing, coating, or sealing render mudstone viable as floor tiles.

Mudstone in Interior Decoration

Interior decoration with mudstone pebble is not a new thing for interior designers. Of course, it depends on the availability of mudstone pebbles in your vicinity and your ability to decorate each piece beautifully.

Exterior Applications

Mudstone is ideal for exterior applications, particularly for landscape and path designs.

Mudstone as Decorative Aggregates

The availability of fossils containing mudrock provides an immense decorative opportunity in your landscape or garden. Creating a water feature by aggregating different looking mudstone is looking a cool idea here. It seems dazzling amongst the colorful plants and foliage in the background.

Mudstone as Building Stones

Since the ancient era, various regions of the world is using mudstone in construction of exterior boundary walls and retaining walls where an abundance of mudrock is found. Combination of Shale and other mudrock gives it natural beauty.

Mudstone as Facing Stones

Mudrock is looking decent when used as stacking stone veneer. Wall facing with stacking stone veneer in the bath and other utility areas is a trend, and mudstone veneer is befitting well in it.

Mudstone as Exterior Pavers

Mudstone aggregates are in the application of construction of various paths in the exterior of a building for centuries. You can use mudstone gravels with appropriate treatments to make walkways smooth and sober even for barefoot walking.

Mudstone as Roof Tiles

Slate is a kind of mudrock and explicitly used as the roof tiles for eons. Mudstone has a property to withstand climatic extremities such as frost, snowfalls, and heavy rains. Mudstone remains cool during burning sunny days.

Mudstone as Stepping Stones

Mudstone as stepping stone in the garden or your wild landscape is a beautiful imagination, and someone has turned it into reality. Shining black to gray hues on irregularly shaped mudstone looks sparkling. The anti-skid surface treatment renders it viable for wet day usage. Water feature with a large mudrock and mudstone aggregates beautifying it further.

Industrial Applications

Apart from construction, mudrock has various industrial or commercial applications.

Cement Manufacturing

The combo of mudrock and limestone is known in the cement manufacturing industry since ancient eras. Our predecessors have burnt both rock aggregates in a Kiln and produced Portland grade cement to constructs large places and monuments famous in history.

Mudstone as Construction Aggregates

Some Shale and other varieties of mudrock are strong enough to provide aggregate use in construction.

Mudstone as Road Aggregates

Mudstone has dual advantages when used as road aggregates. It provides structural elements at micro levels and clay to bind the structure.

Mudstone in Creation of Artistic Objects

Sculpture, figurine, pottery, artwork, and tons of other artifacts in ancient Egyptian monuments are mostly from Mudrock like Shale and Mudstone.


World of Stones USA is a destination to get highly useful information regarding various natural stones useful in exterior applications. A recent effort for mudstone is to add deep knowledge about a less known variety of natural rocks. If you are still thirsty to know more about Mudrock and Mudstone, our natural stone consultants are ready to furnish your demands in explicit ways.


Leave a Comment

Your email address will not be published.