by Q. Identify the Mineral on the basis of the following characteristics relating to it :
UPSC CDS Examination (I) 2025 – General Knowledge
I. It is usually a greenish crystal.
II. It is often found in basaltic rocks.
III. Magnesium, iron and silica are its major elements.
Select the answer using the code given below:
(a) Amphibolite
(b) Feldspar
(c) Pyroxene
(d) Olivine
Answer: (d) Olivine
Explanation:
- Greenish crystal: Olivine is typically olive-green to yellowish-green in colour, which is its most distinctive identifying feature.
- Occurrence in basaltic rocks: Olivine commonly occurs in mafic and ultramafic igneous rocks, especially basalt and peridotite, indicating its mantle origin.
- Chemical composition: Olivine is a magnesium–iron silicate mineral with the general formula (Mg, Fe)₂SiO₄. Hence, magnesium, iron, and silica are its major elements.
Elimination of other options:
- Amphibolite: A metamorphic rock, not a mineral.
- Feldspar: Generally light-coloured and rich in aluminium; not dominated by magnesium and iron.
- Pyroxene: Present in basaltic rocks but usually dark-coloured and less distinctly green compared to olivine.
Answer: (d) Olivine
