The most abundant minerals and mineral groups in sand and silt of soils throughout the world is:
Show Hint
Goldich's weathering series indicates that Quartz is the most stable primary mineral, while Olivine is the least stable.
This explains why Quartz accumulates in sandy soils, while Olivines decompose rapidly.
Step 1: Understanding the Concept:
Soil minerals are classified into primary and secondary minerals based on their origin.
Primary minerals are derived directly from the weathering of parent igneous or metamorphic rocks.
The abundance of these minerals in the sand and silt fractions of soils depends on their initial concentration in the parent rock and their resistance to physical and chemical weathering. Step 2: Detailed Explanation:
Let us compare the mineral properties of the options provided:
- Quartz (\( \text{SiO}_2 \)): Quartz is a primary mineral composed of a continuous framework of silicon-oxygen tetrahedra.
It has no cleavage planes and is highly resistant to both physical abrasion and chemical weathering (such as hydrolysis and dissolution).
Because of this high resistance, while other primary minerals weather away over time, quartz particles accumulate in the coarser fractions of the soil.
Consequently, quartz is the most abundant mineral found in the sand and silt fractions of highly weathered soils worldwide.
- Feldspars: This is the most abundant mineral group in the Earth's crust.
However, because they are susceptible to chemical weathering (hydrolysis), they decompose over time into clay minerals, making them less abundant in weathered sand and silt fractions than quartz.
- Pyroxenes, Amphiboles, and Olivines: These are ferromagnesian minerals that are highly unstable and weather rapidly under humid conditions, making them rare in well-developed soils.
Therefore, Quartz is the most abundant mineral in soil sand and silt. Step 3: Final Answer:
The most abundant mineral in soil sand and silt fractions is Quartz.
