What is the main factor influencing the speed of weathering in rocks?

The main factor influencing the speed of weathering in rocks is indeed the mineral composition of the rocks. Different minerals have varying susceptibilities to weathering processes. For instance, harder minerals, such as quartz, tend to weather more slowly compared to softer minerals like feldspar or calcite, which are more easily broken down by physical and chemical weathering processes.

Additionally, the presence of specific elements within minerals can affect how they interact with environmental factors such as water, temperature, and acids. For example, limestone, which is primarily composed of calcite, is highly susceptible to chemical weathering when exposed to acidic rain, leading to faster degradation.

In contrast, while the color of the rocks, their thickness, and their age may have some influence on their physical characteristics and maybe indirectly relate to weathering rates, they do not play as significant a role as mineral composition does. The mineral composition fundamentally dictates how a rock will respond to various weathering forces, making it the primary factor in the weathering process.