General Course Questions

Question: I have a question about montmorillonite and kaolinite. Based on my notes, Kaolinite is more stable than montmorillonite. I feel confused about that concept. Could you please briefly explain it? Are they both phyllosilicates?

Answer: Yes, both montmorillonite & kaolinite are members of the phyllosilicate group. However, they have a very different crystalline structure, which also translated into different stability and susceptibility to isomorphic substitution. With 2:1 type of structure, montomorillonite is characterized with weaker bonds within its crystallyne structure and is more prone to isomorphic substitutions and consequently larged number of charges than kaolinite (wiht its 1:1 type of structure)

More on these 2 minerals can be found at http://soilweb200.landfood.ubc.ca/soil-components/1-mineral-components/#Types_of_Soil_Colloids as well as in your textbook (see p.240-244)