Weathering of Minerals
There are many factors which influence the weathering of minerals.
1. Climatic conditions
2. Physical characteristics
3. Chemical and structural characteristics
1. Climatic Conditions: The climatic condition, more than any other factor tends to control the kind and rate of weathering. Under conditions of low rainfall, there is a dominance of physical weathering which reduces the size and increases the surface area with little change in volume.
The increase in moisture content encourages chemical as well as mechanical changes and new minerals and soluble products are formed.
The weathering rates are generally fastest in humid tropical regions as there is sufficient moisture and warmth to encourage chemical decomposition.
The easily weather able minerals disappear on account of intense chemical weathering and more resistant products (hydrous oxides of Fe and Al) tend to accumulate
Climate controls the dominant type of vegetation which in turn controls the bio chemical reactions in soils and mineral weathering.
2. Physical Characteristics:
i) Differential composition
ii) Particle size
iii) Hardness and degree of cementation
3. Chemical and structural characteristics:
Chemical: For minerals of given particle size, chemical and crystalline characteristics determine the ease of decomposition. (e.g.) gypsum – sparingly soluble in water, is dissolved and removed in solution form under high rainfall.
Ferro magnesium minerals are more susceptible to chemical weathering than feldspar and quartz
Tightness of packing of ions in crystals: Less tightly packed minerals like olivine and biotitic are easily weathered as compared to tightly packed zircon and muscovite (resistant)