the effects of mineral composition on weathering

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Weathering refers to the breakdown and disintegration and decomposition of rocks in situ through mechanical and chemical changes in rocks and their minerals affected by water,temperature,wind different  atmosphereic gasses etc. provided there is no large scale transport of weathered products by denudational processes except mass movement of rock wastes.
          When the temperature of solid is increased/decreased it expands or contract.the commonly used index in weathering studies to record the degree of their response to temperature changes is called coefficient for linear thermal expansion. It is quite complicated for rocks, particularly at the mineral(crystal) scale. Individual crystals have varying coefficients. Even single crystal coefficients may vary with the direction of measurements. The formula for coefficients for linear thermal expansion is :




moreover, the composition of a mineral surface is not the same as that of the bulk of the mineral, and also varies across the surface caused by attachment of elements from the air/adjacent solutions to an initially highly reactive surface or due to formation of leached layer of the few to several thousand angstroms thick due to the chemical weathering. The atomic structure of the surface of a mineral is frequently not representative of that of the bulk.Typically,surface atoms shift inwards towards the bulk to achieve  a lower-energy arrangement. There are implications for such reactions with external ions.Microtopography also affects weathering response.the most reactive sites in micro topography are where the atoms have the fewest neighbours(i.e., are adatoms) and the least reactive sites are where atoms have the most neighbours(i.e.,trace atoms).

In conclusion it can be said that when we analyse weathering from the perspective of rock composition,temperature acts as a catalyst and acts as a secondary factor in hastening weathering.

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