Why do most sediments that form from weathering consist of silicate minerals?

Rocks are primarily composed of minerals, which are naturally occurring, crystalline solids with a specific chemical composition. Most rocks consist of silicate minerals, which make up about 90% of the Earth's crust. Silicate minerals are characterized by their silica tetrahedron structure (SiO4)^4-, an ion that combines with various metal ions to form different silicate minerals. Common silicate minerals include: - Feldspars (e.g., plagioclase and orthoclase) - Quartz - Mica (e.g., biotite and muscovite) - Amphiboles (e.g., hornblende) - Pyroxenes (e.g., augite)

Weathering is the process by which rocks are broken down into smaller particles and, eventually, soil. This can occur through physical, chemical, or biological means. Physical weathering involves the mechanical breakdown of rocks (e.g., due to temperature fluctuations, ice, or plant roots), whereas chemical weathering results from chemical reactions that alter the minerals within rocks (e.g., dissolution, oxidation, or hydrolysis). Biological weathering often involves both physical and chemical processes, as organisms like lichens and bacteria contribute to the breakdown of rock formations.

Some minerals are more resistant to weathering than others. For instance, quartz is a very stable and weathering-resistant mineral due to its strong, covalent Si-O bonds. In contrast, minerals like feldspars and micas are more susceptible to weathering, as they can be broken down through hydrolysis and other chemical processes. However, even after these more weathering-susceptible minerals break down, many of the weathering products are still silicate-based, such as clay minerals.

As most rocks are initially composed of silicate minerals, it follows that the majority of sediments formed from weathering would also consist mainly of silicates. Moreover, resistant silicate minerals like quartz often survive the weathering process relatively unaltered, becoming important components of sediment deposits. Other silicate minerals may be partially or fully altered during weathering, but many of their weathering products are still silicate-based, contributing to the overall prevalence of silicate minerals in sediments. Additionally, non-silicate minerals such as carbonates may dissolve away during chemical weathering, leaving behind a higher relative proportion of silicate minerals in the remaining sediments. In summary, most sediments formed from weathering consist of silicate minerals due to the initial composition of rocks, the relative stability and resistance to weathering of certain silicate minerals, and the common presence of silicate minerals even among the weathering products of less-resistant silicate minerals.