The most abundant minerals and mineral groups in sand and silt of soils throughout the world is:
Show Hint
Quartz (\(SiO_2\)) is highly resistant to weathering, concentrating in the coarse sand and silt fractions of soil over time.
Feldspars are highly abundant in the Earth's crust but weather much faster than quartz in the soil environment.
Step 1: Understanding the Concept:
The mineral composition of the sand and silt fractions of soils depends on the mineralogy of the parent rock and the resistance of those minerals to chemical and physical weathering over time. Step 2: Detailed Explanation:
Let us analyze the weathering resistance and abundance of soil minerals:
- Quartz (\(SiO_2\)): This is a tectosilicate mineral made of highly stable silicon-oxygen tetrahedra arranged in a continuous framework.
It contains no weak ionic cleavages and is highly resistant to both chemical weathering (such as hydration, hydrolysis, or carbonation) and physical abrasion.
During soil development, more soluble minerals (like olivine, pyroxenes, and feldspars) weather and wash away first, leaving behind highly stable quartz grains.
Consequently, quartz concentrates in the coarser soil separates, making up \(90\%\) to \(95\%\) of the total mineral content in the sand and silt fractions of most mature soils worldwide.
- Feldspars: Although feldspars are the most abundant mineral group in the Earth's crust, they are moderately susceptible to chemical weathering and break down to form clay minerals (like kaolinite), making them less abundant in the sand and silt fractions than quartz.
- Olivines, Pyroxenes, and Amphiboles: These are dark ferromagnesian minerals that weather very rapidly under humid conditions, meaning they are found only in trace amounts in mature soil sand fractions.
Therefore, the most abundant mineral in sand and silt is quartz. Step 2: Final Answer:
The most abundant mineral in sand and silt of soils throughout the world is quartz.
