Thus, quartz has a very low solubility. Because it is also hard, resists abrasion, and is a common primary mineral in many rocks, it is a common constitute of soils. As figure 11.1, clearly shows, the secondary minerals that result from weathering processes depend directly on the nature of the primary minerals and hence the type of underlying bedrock. The typical weathering products of a granite are given in Table 11.1 and show that in chemical weathering, many reactions are taking place simultaneously. It is also important to note that many of the rocks exposed at the surface of the earth are sediments that are already made largely of the secondary minerals in Fig.
Climate is second only in importance to parent material as a controlling factor in soil formation.
The climate controls weathering and soil formation directly, through the amount of precipitation and the temperature, and indirectly through the kinds of vegetation that can cover the land. Hot arid climates allow for the growth of little vegetation and provide too little water to permit much chemical weathering. Consequently, such regions often do not develop true soils. Weathering involves rapid mechanical and chemical breakdown of the less resistant silicates. Clays may be blown away to leave only sands made up largely of quartz.