[Geography Notes] on Clay Mineral Pdf for Exam

Clay minerals are the hydrous aluminium phyllosilicates that are available at times with varying amounts of iron, alkali, metals, magnesium, alkaline earth, and such other cations. They are generally found on or near some planetary surfaces. Clay minerals are formed mainly in the presence of water. They are proved to be very important to our life. Other theories of abiogenesis are involved in them. With them, they carry important constituents of the soils which have been beneficial to humans since time immemorial. 

 

In this Section, we will know about Various Types of Clay and Their Constituents. 

Kaolinite Clay or China Clay

The clay mineral is termed Kaolinite which has Al₂Si₂O5(OH)4 as its chemical composition. Kaolinite Clay is very much important as an industrial mineral. Kaolinite is a layered mineral of silicate coupled with silica which is SiO4, this is further linked through the oxygen atoms to an octahedral sheet of the alumina (AlO₆) octahedra. Rocks that are rich in kaolinite are called the kaolin or also known as China Clay. 

Bentonite

Bentonite is a type of absorbent swelling clay which majorly consists of montmorillonite.  This type of clay usually is formed from the weathering of the volcanic ash in the presence of seawater, after which it converts into volcanic gases that are present in the ash and clayey minerals. The Bentonite beds are white or pale blue or green in colour when exposed to fresh exposures, they can also turn to a cream colour and after which they can turn into yellow, red, or brown as the exposure is more.  

Montmorillonite

Montmorillonite is a very soft mineral that comes under the group of phyllosilicate minerals. These mineral forms when they precipitate from the water solution in the form of microscopic crystals. Called clay. This clay is named after Montmorillon in the country France.  The clay is in the ratio of 2:1, which means that it has two tetrahedral sheets of silica and a single octahedral sheet of the alumina. The particles are featured as plate-shaped with an average diameter of around 1 micrometer and have a thickness of about 0.96 nm. 

Powdered Bentonite

Bentonite clay is used by human beings to remove impurities on their skin, like oils, and other toxins from the body. This practice is done for thousands of years. Bentonite clay is also present in many skincare products. While some people also add this to foods or drinks with the aim to improve digestive issues or to remove toxins from the body.

Types of Clays

The main four types of clay are as follow:

• Earthenware clay

• Stoneware clay

• Ball clay

• Porcelain. 

All of these clays are used to make pottery. These seem all same but the texture, colour, and flexibilities differ a great deal.  

Tosudite

Magnesium Tosudite is a clay mineral with a 1:1 ratio interstratification of the compound name trioctahedral Mg chlorite and Sudoite and also dioctahedral Smectite.

Smectite

Smectite is also a clay mineral (like bentonite) that undergoes reversible expansion while absorbing the water.

Sepiolite

Sepiolite is the English name, while in German it is known as meerschaum which means ‘sea foam’. This is soft textured while clayey mineral which is often used in making tobacco pipes also called the meerschaum pipes. This is a complex magnesium silicate which is a specific chemical formula Mg4Si6O15(OH)2·6H2O, this can be present in the fibrous, fine-particulate, and solid forms.

Pyrophyllite

Pyrophyllite is a type of mineral which is phyllosilicate and this is composed of aluminium silicate hydroxide, the chemical formula which is Al2Si4O10(OH)2. This occurs in two forms crystalline folia and the form of compact masses, while there are distinct crystals as well which are well known.  

Pyrophyllite which occurs in the phyllite and schistose rocks is generally associated with kyanite used as an altered product.

Ball Clay

Ball clays are made up of kaolinitic sedimentary clays which are commonly constituted with 20–80% of kaolinite, 10 to 25% mica 6 to 5% of quartz. The localized seams in the same deposit have variations in their composition, this includes the quantity of these major minerals, which are accessorized minerals and carbonaceous materials like lignite. They form fine-grained and quite is quite plastic in nature, and this is unlike the earthenware clay. They produce fine quality pottery with white colour body.