Kaolinite — behavior and identification: Which of the following statements about kaolinite clay minerals are correct?

Introduction / Context:
Clay mineralogy strongly influences engineering behavior. Kaolinite, illite, and montmorillonite (smectite) form a useful trio when contrasting swelling, plasticity, and stability characteristics. Kaolinite is widely encountered in residual and transported soils, ceramics, and paper industries (as China clay).

Given Data / Assumptions:

• Kaolinite has a 1:1 layer structure (one silica tetrahedral sheet bonded to one alumina octahedral sheet).
• Interlayer bonding is relatively strong (hydrogen bonding), restricting water entry.
• Surface carries net negative charge, attracting water and cations.

Concept / Approach:
Because interlayer spacing is fixed by strong bonds, kaolinite exhibits minimal swelling compared with smectites. It remains relatively stable under wetting–drying cycles and shows moderate plasticity. Industrially, purified kaolinite is referred to as China clay and is valued for whiteness and plate-like particles.

Step-by-Step Solution:

Verification / Alternative check:
Compare with montmorillonite (smectite), which displays large swelling and high plasticity; kaolinite’s restrained behavior confirms the above statements.

Why Other Options Are Wrong:
Each individual statement A–D is correct; therefore “All the above” is the most complete and accurate choice.

Common Pitfalls:
Assuming all clays swell significantly; kaolinite is an important counterexample with low swell potential and relatively predictable engineering behavior.

Final Answer:
All the above