Question

Weathering Index of Kaolinite is _______

• A. 10
• B. 8
• C. 7
• D. 9

Hint:

Remember the classic clay mineral sequence in Jackson's weathering index: Illite (Stage 7) $\to$ Vermiculite (Stage 8) $\to$ Smectite (Stage 9) $\to$ Kaolinite (Stage 10) $\to$ Gibbsite (Stage 11). Higher index values represent more highly weathered soils.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
M. L. Jackson (1948) proposed a weathering index system consisting of 13 stages based on the mineral composition of clay fractions.
Minerals are assigned to specific weathering stages (1 to 13) depending on their relative stability and resistance to weathering.

Step 2: Detailed Explanation:
Let us review the key stages of Jackson's weathering index:
Stage 1: Gypsum
Stage 2: Calcite
Stage 3: Olivine-Hornblende
Stage 4: Biotite
Stage 5: Albite
Stage 6: Quartz
Stage 7: Illite (Muscovite)
Stage 8: Vermiculite
Stage 9: Smectite (Montmorillonite)
Stage 10: Kaolinite
Stage 11: Gibbsite (Al-oxides)
Stage 12: Hematite (Fe-oxides)
Stage 13: Anatase (Ti-oxides)
Kaolinite is a stable 1:1 clay mineral that forms under advanced weathering conditions.
It is assigned to Stage 10 of the weathering index, representing highly weathered soils.

Step 3: Final Answer:
The weathering index of Kaolinite is 10, which corresponds to option (A).