Claystone – What Is Claystone and How It Formed

Claystone – What Is Claystone and How It Formed

Mar 28, 2023

Claystone is a clastic form of sedimentary rock. It primarily consists of tiny particles cemented into hard rock with a size of less than 1/256 mm.

In terms of size, Claystone is comparable to siltstone and Mudstone. Therefore, Claystone’s formation is similar and useful to Mudstone. A brief idea regarding Claystone facts and applications are provided in this article.

Mudstone, Siltstone/ Shales, and Claystone are frequently used interchangeably. From the perspective of geology, each is unique.

How to Distinguish Claystone?


Shales or siltstone is containing more than half of the composition made from silt-sized particles, such as

  • Coarse silt – 1/32mm (5Phi-Ø)
  • Fine silt – 1/64mm (6Phi-Ø)
  • Very fine silt – 1/128mm (7Phi-Ø)

Siltstone breaks into thin chips, which are roughly parallel from top to bottom.


Claystone is containing more than half of the composition made from clay-sized particles – 1/256mm (8Phi-Ø). We will see more details in the next section.

Mudstone:It is a mixture of silt and clay size particles and forms a bit hardened mud. Mudstone breaks into rocky pieces. 

Geological Definition & Classification of Claystone:

At the geological perspectives, claystone can define in the following ways. 

Class Sedimentary rocks
Sub-class Durable & medium hardness rock
Categories Fine-grained & opaque rock
Types Lithified and non-fissile rocks
Species 35 recognized clay minerals exist.

The Texture of Claystone: 

Texture Clastic
Color  Black, Blue, Brown, Green, Grey, Orange, Red, White, Yellow, 
Durability  Durable 
Water-resistant  Yes 
Scratch-resistant  Yes 
Stain-resistant  No 
Acid-resistant  No 
Wind resistant  No 
Appearance  Rough & Dull 

Properties of Claystone:

At the general and geological perspectives, claystone has the following properties. 

Hardness 3.5 to 4.0
Grain size Less than 1/256mm
Streak White
Porosity Less
Toughness 2.6
Cleavage  Perfect
Density 2 to 2.9 G/cm3
Specific Heat Capacity 0.92 KL/Kg K
Resistance Heat & Impact 

Composition of Claystone:

Mineral content Biotite, Chlorite, Feldspar, Micas, Muscovite or Illite, Plagioclase, Pyrite, & Quartz
Compound content Aluminum Oxide, Ca, NaCl, CaO, Iron(III) Oxide, MgO, & Silicon Dioxide
Weathering Biological Weathering, Chemical Weathering, & Mechanical Weathering
Erosion  Coastal erosion, water erosion & wind erosion
Formation It is soft but can be hard and brittle. Formation takes place due to the weathering of mudstone.

Reserves of Claystone 

Claystone availability is universal and found mainly in the following regions and countries.

Bald Hill at Long Reef. New South Wales, Australia

Asia India, China, Bangladesh, & Russia
Africa South Africa, Ethiopia, Tanzania, Morocco, & Kenya
Europe Scotland, France, Austria, Germany, Italy, Greece, Spain, Romania, & Switzerland
North America Canada, Panama, & USA
South America Colombia, Bolivia, Chile, Peru, Ecuador, & Venezuela
Australia New South Wales, New Zealand, Queensland, Victoria, Western Australia

Katoomba, Australia

Claystone Formation

Clay particles are fine-grained and nearly 1/1000 times finer than a standard sand particle of 1mm size. Water carries claystone particles 100 times farther than the sand particles when it flows.

Moreover, the sedimentation of claystone particles requires a relatively calm milieu at the water basins in the river and sea. Thereby, due to heavyweight sandstone found at more profound layers of sediment strata. 

Whereas thin layers of the Claystone are found on the top and primarily in between siltstone layers. It is due to almost similar particle sizes of siltstone and Claystone.

Applications of Claystone 

Claystone has interior as well as exterior applications in the construction industry. Architects also prefer Claystone in the creation of proper curbing appeal. Apart from these, the manufacturing applications of Claystone are far broader than we anticipate in the direct constructions.

For instance, 

  • Claystone is helpful in the steel industry in processing Iron Ore by acting as a sintering agent.
  • Claystone provides raw material in cement manufacturing units to make natural cement and create the mortar.
  • Claystone is a good stone aggregate material for the road building industry.

Let’s see some good examples of the applications of Claystone as a direct construction.

Claystone Aggregates in Interior & Exterior Decoration

You can use claystone aggregates, pebbles for garden, and boulders to decorate your interior and exterior spaces like wall coverings, floors, and window sills. You will find claystone aggregates and pebbles in various shapes and colors, albeit with natural beauty.

Claystone Aggregates in Garden Decoration

You can decorate your garden with claystone pebbles and stone aggregates. Paths, planters, and decorative pieces of the garden landscape are ideal spaces to use colorful claystone pebbles and aggregate to beautify your gardens and outdoor landscapes.

Claystone as Facing Stone

Claystone Facing Bricks  

Bricks from Claystone is a modern approach in the construction industry, and China is famous for it. Many stone veneer producers create claystone veneers as facing bricks, providing a decent opportunity to decorate your exterior facing walls.

Claystone in Entryway

Claystone Raw Tiles Claystone Façade 

Raw claystone tiles were used in ancient days, and many have kept the tradition alive by decorating their facade with claystone tiles from floors to entryways and even on the walls to match a theme. Claystone powder is also fashionable to decorate exterior walls to create a classic look-n-feel.

Claystone in Roofing

Like slatestone, many areas in Asian countries use claystone roof tiles in very primitive formats. Such traditions help people leverage natural offerings of claystone material in many ways.

Find Your Claystone Inventory

World of Stones USA has an extensive stock of claystone inventory to use in your modern construction and give a classic touch augmenting aesthetic appeal. You can find the best stone consulting services to know where you can apply Claystone in your next project and how it could be a feasible adventure for you. 


This informative guide on Claystone might have helped you understand this stone better. Our claystone products are available across the country, thanks to our expanded distribution network and an extensive list of distributors.



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