Consider the following minerals:

1. Bentonite

2. Chromite

3. Kyanite

4. Sillimanite

In India, which of the above is/are officially designated as major minerals?

The correct option is 2, 3 and 4 only.

Step-by-Step Explanation:

1. Understanding Mineral Classification in India:
In India, minerals are classified into "minor minerals" and "major minerals" under the Mines and Minerals (Development and Regulation) Act, 1957 (MMDR Act). While the term "major mineral" is not explicitly defined in the act, any mineral that is not declared as a "minor mineral" under Section 3(e) of the MMDR Act is by default treated as a major mineral.

2. Analyzing the Given Minerals:
- Bentonite (1): Bentonite is a type of clay. In India, it is officially notified and designated as a minor mineral. The state governments have the authority to frame rules for minor minerals.
- Chromite (2): Chromite is a principal ore of chromium and is used extensively in metallurgical industries (like stainless steel production) and chemical industries. It is officially classified as a major mineral.
- Kyanite (3): Kyanite is an aluminosilicate mineral used in refractories, ceramics, and other high-temperature applications. It is designated as a major mineral.
- Sillimanite (4): Sillimanite is another aluminosilicate mineral, closely related to kyanite, also primarily used in the manufacturing of refractories. It is classified as a major mineral.

3. Conclusion:
Among the given list, Chromite (2), Kyanite (3), and Sillimanite (4) are officially designated as major minerals, whereas Bentonite (1) is designated as a minor mineral. Therefore, the correct combination is 2, 3 and 4 only.