The key difference between kaolinite and montmorillonite is that kaolinite consists of one aluminium octahedral sheet and one silica tetrahedral sheet whereas montmorillonite mineral has two silica tetrahedral sheet and an aluminium octahedral sheet per repeating unit.
Kaolinite and montmorillonite are clay minerals. These minerals have their chemical structures as sheets stacked on each other in different ratios.
CONTENTS
1. Overview and Key Difference
2. What is Kaolinite
3. What is Montmorillonite
4. Side by Side Comparison – Kaolinite vs Montmorillonite in Tabular Form
5. Summary
What is Kaolinite?
Kaolinite is a type of clay mineral having the chemical composition Al2SiO2O5(OH)4. It is a group of industrial minerals that occurs as a layered silicate mineral with one tetrahedral sheet of silica that is linked through oxygen atoms to another octahedral sheet of alumina. Usually, the term kaolin is used to refer to rocks that are rich in kaolinite. China clay is another name for this type of rocks.
The category of kaolinite is phyllosilicates, and this material has a triclinic crystal system. It appears in white to cream colour, but sometimes we can observe red, brown or blue tints that come from the presence of impurities. Moreover, it rarely occurs as crystals, but it is mostly in a plate-like structure that is stacked to form the overall structure. This mineral has a pearly lustre and the mineral streak is white.
Kaolinite has several important properties, such as low shrink swell capacity and low cation exchange capacity. Also, this mineral is a soft, earthy mineral that is usually white coloured. Kaolinite is formed from the weathering of aluminium silicate minerals such as feldspar.
There are many different uses of kaolinite mineral such as the production of paper, ceramics, toothpaste, cosmetics, production of insulating materials such as kaowool, paints, for modification of the properties of rubber upon vulcanization, in organic farming as a spray, etc.
What is Montmorillonite?
Montmorillonite is a type of clay mineral that has the general formula (Na,Ca)0.33(Al,Mg)2(Si4O10)(OH)2.nH2O. This mineral belongs to the group of phyllosilicates. The crystal system of this material is monoclinic, and the appearance can be described as white, pale pink to red. The fracture of this mineral is uneven. The lustre is dull and earthy. When considering the chemical structure, this material has two tetrahedral sheets of silica, sandwiching a central octahedral sheet of alumina.
There are different uses of montmorillonite. It is used in the dilling industry as a component of drilling mud which helps to make the mud slurry viscous. Also, this material is useful as a soil additive to hold soil water in drought-prone soils. This mineral is very useful in catalytic processes such as catalytic cracking. In addition to that, montmorillonite has a swelling property which makes it important as an annular seal or plug for water wells and as a protective liner for landfills.
What is the Difference Between Kaolinite and Montmorillonite?
Kaolinite and montmorillonite are clay minerals. These minerals have their chemical structures as sheets stacked on each other in different ratios. The key difference between kaolinite and montmorillonite is that kaolinite consists of one aluminium octahedral sheet and one silica tetrahedral sheet whereas montmorillonite mineral has two silica tetrahedral sheet and an aluminium octahedral sheet per repeating unit.
Moreover, kaolinite is usually white to cream in colour while montmorillonite is white, pale pink to red in colour.
Below infographic shows more differences between kaolinite and montmorillonite.
Summary – Kaolinite vs Montmorillonite
Kaolinite and montmorillonite are clay minerals. These minerals have their chemical structures as sheets stacked on each other in different ratios. The key difference between kaolinite and montmorillonite is that kaolinite consists of one aluminium octahedral sheet and one silica tetrahedral sheet whereas montmorillonite mineral has two silica tetrahedral sheet and an aluminum octahedral sheet per repeating unit.
Reference:
1. “Kaolinite.” Wikipedia, Wikimedia Foundation, 29 Aug. 2020, Available here.
Image Courtesy:
1. “Kaolinite from Twiggs County in Georgia in USA” By James St. John (CC BY 2.0) via Commons Wikimedia
2. “Montmorillonite-Quartz-pala48a” By Rob Lavinsky, iRocks.com –(CC BY-SA 3.0) via Commons Wikimedia