Weathering is a complex interaction of physical, chemical and biological processes that alters the stone in some general or specific way.

The physical properties of stone differ widely between stone groups and even within the same stone type. The mineral composition, textural differences, varying degrees of hardness and pore/capillary structure are the main reasons why not all the surface of the same stone shows signs of alteration the same and evenly.

These minerals can be broken down, dissolved or converted to new minerals by a variety of processes which are grouped as Mechanical and Chemical.

It’s the sum the of these factors that determines the type and rates which dimensional stone  will be affected by the chemical weathering processes.

There is another aspect to the natural weathering / alteration process which is often misunderstood.
This involves understanding that some stones due to their natural characteristics will naturally experience some sort of appearance change.

One example of this is some limestone will develop a patina which actually gives the stone more character and offers a certain amount of protection as well.
However, the prevailing mindset that has been developed by the consistent uniform appearance of manmade and synthetic building materials fosters the idea that something wrong is happening with its appearance.  It should be understood that what is taking place in this particular situation is a natural occurring process.

It needs to be emphasized, that all stone will experience the natural weathering process to a certain degree. However, understanding the natural characteristics of the stone and the weathering processes that affect them, proper maintenance and preservation programs can be employed to minimize and manage their effects.