Clay Mineralogy

Clay Mineralogy  

  1. Important clay minerals kaolinite, Illite, montmorillonite  and halloysite, are present in clays. 
  2. In coarse grained soils, like gravel, sand, rock minerals  like quartz, feldspar, mica, etc., are present. 

Kaolinite Mineral  

  1. One molecule of kaolinite mineral is made of one silica  sheet and one gibbsite sheet.  
  2. Various such molecules are joined by hydrogen bonds.  
  3. These show less change in volume due to changes in  moisture content.  
  4. Kaolinite is thus the least active of clay minerals. 

Montmorillonite Mineral 

  1. One molecule of montmorrilonite mineral is made of two  silica sheets and one gibbsite sheet.  
  2. Gibbsite sheet is sandwiched between silica sheets. 
  3. Various such molecules are loosely bonded through water.  
  4. These soils show high volume changes on moisture variation (i.e., large swelling and large shrinkage). 

Diffuse Double Layer and Adsorbed Water  
  1. Clay particles usually carry a negative charge on their  surface.  
  2. Because of net negative charge on the surface, the clay  particles attract cations, such as potassium, calcium and  sodium, from the moisture present in the soil to reach  equilibrium.  
  3. The layer extending from the clay particle surface to the  limit of attraction is known as a diffuse double layer.  
  4. The water held in the zone of the diffuse double layer is  known as adsorbed water or oriented water.  
  5. The plasticity characteristics of clay are due to the presence of adsorbed water.  
  6. Clays using non-polar liquid, such as kerosene in place of  water, does not show any plasticity characteristics.  
  7. The thickness of adsorbed water layer is about 10–15A°  for colloids, but may be up to 200A° for silts. 


Clay Mineralogy Clay Mineralogy  Reviewed by Parag Pal on 11:23 AM Rating: 5

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