Here's why:
* Mica: Mica is a sheet silicate mineral. It has a layered structure with weak bonds between the layers. This layering makes it susceptible to exfoliation, where the layers peel away like pages in a book due to changes in temperature, pressure, or moisture.
* Shale: Shale is a fine-grained sedimentary rock composed primarily of clay minerals. These minerals, like mica, have a layered structure. Exfoliation in shale often occurs along the bedding planes (the original layering of the sediment), resulting in the rock breaking into thin slabs.
Other types of physical weathering that can affect Mica and Shale:
* Frost wedging: While not as common as exfoliation, frost wedging can occur in areas with freezing temperatures. Water seeps into cracks, freezes, expands, and puts pressure on the rock, eventually causing it to break.
* Abrasion: This can occur when rocks are moved by wind or water, and the friction causes them to break down. Abrasion can also happen when rock fragments are carried within glaciers, grinding against other rocks.
* Root wedging: Plant roots can grow into cracks in the rock, expanding and putting pressure on the rock, leading to its breakage.
Note: Exfoliation is the most prominent weathering process for Mica and Shale due to their layered structures and inherent weakness along these layers.
