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?

[UPSC Civil Services Exam – 2020 Prelims]

(a) 1 and 2 only

(b) 4 only

(c) 1 and 3 only

(d) 2, 3 and 4 only

Answer: (d)

Explanation:

• As per Govt. of India Notification S.O. 423(E) dated 10^th February 2015 Bentonite has been declared as ‘Minor Mineral’.
• The minor minerals which have been declared by the Central Government include boulder, shingle, chalcedony pebbles (specifically for ball mill purposes), lime shell, kankar, limestone (used in kilns for making lime which is a building material), murrum, brick-earth, fuller’s earth, bentonite, road metal, reh-matti, slate, shale (when utilized for construction purposes), marble, stone (for household utensils), quartzite, sandstone (for building or making road metal and household utensils), saltpeter, and ordinary earth (used for filling or leveling purposes in construction, embankments, roads, railways, and building).
• The mineral Bentonite is predominantly composed of montmorillonite, a clay mineral that makes up at least 85% of its composition and gives it its highly plastic nature.
• Chromite (Cr) is the only ore of chromium that has commercial viability, and it is chemically referred to as iron chromium oxide (Fe.Cr₂O₄).
• On the other hand, Kyanite, Sillimanite, and Andalusite are minerals that contain anhydrous aluminosilicate and share the same chemical formula (Al₂O₃), but differ in physical properties and crystal structure.

Therefore, option (d) is the correct answer.