Question

Arrange the minerals in the order of increasing weathering index
(A).Quartz
(B).Gypsum
(C).Haematite
(D).Allophane
Choose the correct answer from the options given below:

• A. (A), (B), (C), (D).
• B. (A), (C), (B), (D).
• C. (B), (A), (D), (C).
• D. (C), (B), (D), (A).

Hint:

To solve mineral weathering questions quickly:
Soluble salts (gypsum, calcite) are always at the beginning of the index.
Primary silicates (quartz) are in the middle.
Secondary clay minerals (allophane, kaolinite) are near the end.
Insoluble oxides (hematite, anatase) are at the absolute end.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Weathering is the physical disintegration and chemical decomposition of minerals and rocks at the earth's surface.
Different minerals exhibit varying degrees of resistance to chemical weathering.
Jackson et al. (1948) proposed a weathering index consisting of 13 stages.
This index groups soil minerals from the most easily weathered (Stage 1) to the most resistant (Stage 13).

Step 2: Detailed Explanation:
Let us analyze the position of the given minerals in Jackson's weathering index:
- (B) Gypsum: An extremely soluble calcium sulfate mineral.
It is highly susceptible to dissolution and chemical weathering, placing it at Stage 1 (least resistant).
- (A) Quartz: A highly resistant primary silicate mineral with a stable framework structure.
It is placed at Stage 6 of the weathering index.
- (D) Allophane: An amorphous, poorly crystalline aluminosilicate secondary clay mineral.
It represents a highly weathered secondary stage, placed at Stage 10.
- {(C) Haematite: An insoluble iron oxide (\( \text{Fe}_2\text{O}_3 \)) secondary mineral.
It represents the advanced stages of desilication and oxide accumulation, placing it at Stage 12 (highly resistant).
Arranging these minerals in order of increasing weathering index (least resistant to most resistant) gives:
\[ \text{Gypsum (B)} \rightarrow \text{Quartz (A)} \rightarrow \text{Allophane (D)} \rightarrow \text{Haematite (C)} \]
This matches the sequence (B), (A), (D), (C), corresponding to Option (C).

Step 3: Final Answer:
The correct sequence in order of increasing weathering index is (B), (A), (D), (C).