Home Sedimantery Rocks Non-Clastic Sedimentary Rock Mudstone

Mudstone

SHARE

Mudstone is a really pleasant-grained sedimentary rock consisting of a aggregate of clay and silt-sized particles. Terms including claystone and siltstone are often used in location of mudstone, although these consult with rocks whose grain length falls inside a good deal narrower stages and underneath near exam those are frequently technically mudstones. Shale is frequently used to explain mudstones that are difficult and fissile (wreck along bedding planes). Marl is regularly used to explain carbonate-rich tender mudstones.

Texture: Clastic Sedimentary Rock
Grain size: Very fine-grained (< 0.06mm); clasts not visible to the naked eye.
Hardness: Generally quite soft, but can be hard and brittle.
Colour – variable – black, white, grey, brown, red, green, blue etc.
Clasts: Generally a mixture of clay minerals with any or all of quartz, feldspar ( orthoclase,plagioclase), mica ( biotite, chlorite, muscovite); can contain iron oxides (cause red or yellowish colouring); black colouring due to carbonaceous content and / or pyrite.
Other features – smooth to touch.

Mudstone can be separated into these categories:

Clastic sedimentary rocks are classified by size of the sediment particles making up the rock. Particle size descriptions like sand, silt, and clay have specific meaning in geology and engineering.

Shales, mudstones and claystones are rock types that are very similar to each other.

  • Siltstone – more than half of the composition is silt-sized particles.
  • Claystone – more than half of the composition is clay-sized particles.
  • Mudstone – hardened mud; a mix of silt and clay sized particles.

The difference between mudstone and shale is that mudstones break into blocky pieces whereas shales break into thin chips with roughly parallel tops and bottoms.

The terms shale and claystone are sometimes used interchangeably.

Siltstone 

As its name implies, it is primarily composed (greater than 2/3) of silt sized particles, defined as grains 2–62 µm- more than half of the composition is silt-sized particles.

Siltstone
Siltstone 

Claystone

A claystone is lithified, and non-fissile mudrock. In order for a rock to be considered a claystone, it must consist of up to fifty percent clay, which measures less than 1/256 of a millimeter in particle size  — more than half of the composition is clay-sized particles.

Claystone
Claystone

Mudstone 

Mudstones and shales are made of silt- and clay-sized particles that are too small to see. The only difference between mudstone and shale is that mudstones break into blocky pieces whereas shales break into thin chips with roughly parallel tops and bottoms. Both are made of ancient mud.

Shale: Exhibits lamination or fissility.

Shale is a fine-grained, clastic sedimentary rock composed of mud that is a mix of flakes of clay minerals and tiny fragments (silt-sized particles) of other minerals, especially quartz and calcite. Shale is characterized by breaks along thin laminae or parallel layering or bedding less than one centimeter in thickness, called fissility. It is the most common sedimentary rock

Argillite: It has undergone low-grade metamorphism.

Argillaceous rocks are basically lithified muds and oozes. They contain variable amounts of silt-sized particles. The argillites grade into shale when the fissile layering typical of shale is developed. Another name for poorly lithified argillites is mudstone. These rocks, although variable in composition, are typically high in aluminium and silica with variable alkali and alkaline earth cations. The term pelitic or pelite is often applied to these sediments and rocks. Metamorphism of argillites produces slate, phyllite, and pelitic schist

Cite this article as: Geology Science. (2019). Mudstone. [online] Available at: http://geologyscience.com/rocks/sedimantery-rocks/mudstone/ [5th December 2019 ]
SHARE