Which weathering type involves alteration of minerals within the rock structure?

The process that involves the alteration of minerals within the rock structure is known as chemical weathering. This type of weathering occurs when rocks undergo chemical reactions that result in changes to their mineral composition and structure. For example, when rainwater, which is slightly acidic due to dissolved carbon dioxide, reacts with feldspar in granite, it can convert the feldspar into clay minerals. Such transformations not only change the mineralogy of the rock but can also lead to the breakdown of the rock into finer particles.

In contrast, physical weathering focuses on the mechanical processes that break down rocks into smaller pieces without changing their mineral composition. This includes actions like freeze-thaw cycles, where water enters cracks in the rock, freezes, and expands, ultimately causing the rock to fracture. Biological weathering involves living organisms, such as plants and their roots, which can contribute to the disintegration of rocks but does not fundamentally alter the minerals. Mechanical weathering, while similar to physical weathering, emphasizes the physical forces applied to the rock without any chemical change. Thus, chemical weathering is specifically characterized by the alteration of the minerals within the rock itself.