What is a critical factor in the susceptibility of rocks to spheroidal weathering?

Spheroidal weathering is a process primarily influenced by the mineral composition of rocks, particularly the presence of feldspar. Feldspar is a key component of many igneous and metamorphic rocks and is more susceptible to chemical weathering compared to quartz. During spheroidal weathering, the corners and edges of rock blocks weather more quickly, leading to rounded shapes. This process is enhanced by the presence of feldspar, which undergoes hydrolysis, resulting in the transformation of feldspar minerals into clay minerals.

The increased susceptibility of feldspar to weathering compared to other minerals like quartz, which is much more resistant to both chemical and physical weathering, makes it a critical factor in this weathering process. Additionally, the resulting clay minerals contribute to the alteration of the rock, facilitating further weathering and rounding.

While the amount of quartz and the layering of rocks can influence the weathering process, they do not play the same crucial role in spheroidal weathering as feldspar does. The type of soil may impact the overall environment and weathering rates, but it is not a direct factor in the rock's susceptibility to becoming rounded through spheroidal weathering. Understanding the behavior of different minerals under weathering conditions is essential