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

Explanation:

Minerals Classification in India

In India, minerals are classified into two main categories: major minerals and minor minerals. The classification is based on the Mines and Minerals (Development and Regulation) Amendment Act, which was last amended in 2015. The distinction between major and minor minerals is significant in terms of the regulatory and administrative framework governing their extraction and management.

1. Bentonite

Bentonite is primarily a type of clay mineral, known for its ability to swell and absorb water, making it useful in various industrial and health applications. It is generally considered a minor mineral in India.

2. Chromite

Chromite is an important ore of chromium, which is used in stainless steel, nichrome, and chrome plating. Given its economic importance, chromite is classified as a major mineral.

3. Kyanite

Kyanite is an aluminum silicate mineral used in the manufacture of refractory materials, capable of withstanding high temperatures. It is valuable for industries that require materials with high thermal resistance. Kyanite is classified as a major mineral in India due to its economic importance and specific industrial uses.

4. Sillimanite

Sillimanite is also an aluminum silicate mineral used in the manufacture of refractory materials, capable of withstanding high temperatures. It is valuable for industries that require materials with high thermal resistance. Sillimanite is classified as a major mineral in India due to its economic importance and specific industrial uses.

Therefore, the correct answer to the question is:

d) 2, 3, and 4 only