Question

The characteristics of Palygorskite mineral are..
(A). They are found in Humid regions
(B). They have fibrous morphology
(C). They are Amphibole double silica chain
(D). They form double ribbed sheet with two rows of tetrahedral apexes
Choose the correct answer from the options given below:

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

Hint:

Palygorskite and sepiolite are the two main fibrous clay minerals.
They are stable in arid, alkaline environments and are characterized by their needle-like or fibrous structures rather than flat plates.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Clay minerals are classified based on their crystalline structure and layer arrangement into phyllosilicates (sheets) or fibrous silicates.
Palygorskite (also known as attapulgite) is a magnesium aluminum silicate clay mineral with a unique structure that differs from typical sheet silicates like montmorillonite or kaolinite.

Step 2: Detailed Explanation:
Let us analyze the characteristics of palygorskite:
- Environmental distribution (A): Palygorskite is typically found in arid and semi-arid regions under alkaline conditions with high magnesium and calcium activity.
It is not stable in humid regions, where intense weathering and leaching remove alkaline cations. Thus, (A) is incorrect.
- Morphology (B): Unlike typical flat-plated clay minerals, palygorskite has a distinct fibrous morphology, forming lath-like or needle-like crystals. Thus, (B) is correct.
- Crystalline structure (C): Its structure is intermediate between phyllosilicates and inosilicates.
It is composed of amphibole-like double silica chains linked by octahedral magnesium/aluminum sheets, forming long channels. Thus, (C) is correct.
- Tetrahedral arrangement (D): The continuous tetrahedral sheets are periodically inverted, forming a double-ribbed sheet with two rows of tetrahedral apexes pointing in opposite directions.
This structure creates open channels, giving the mineral a high surface area and absorption capacity. Thus, (D) is correct.
Therefore, characteristics (B), (C), and (D) are correct.

Step 3: Final Answer:
The correct combination is (B), (C), and (D) only.