UPSC Prelims 2001 Q122: Geography – Physical Geography & Geomorphology
Quartzite is metamorphosed from
- (a) Limestone
- (b) Obsidian
- (c) Sandstone
- (d) Shale
Answer: (c) Sandstone
Explanation
Rock from which quartzite is metamorphosed
| Original rock | Metamorphic rock |
|---|---|
| Sandstone | Quartzite |
| Limestone | Marble |
| Shale | Slate (then schist) |
| Granite | Gneiss |
Quartzite forms when sandstone, made of quartz grains, is heated and pressed until the grains fuse. Limestone becomes marble and shale becomes slate. Obsidian is volcanic glass, an igneous rock.
Answer: (c) Sandstone.
Why each option is right or wrong
- (a) Incorrect. Limestone changes into marble.
- (b) Incorrect. Obsidian is volcanic glass, not the parent of quartzite.
- (c) CORRECT. Sandstone changes into quartzite.
- (d) Incorrect. Shale changes into slate.
Key point
Quartzite is very hard and resistant; it forms ridges such as parts of the Delhi Ridge and the Aravallis.
Remember
Sandstone → quartzite; limestone → marble; shale → slate.
Common mistakes
- Mixing up the parents of marble and quartzite.
- Choosing shale, which becomes slate, not quartzite.
- Thinking obsidian is a sedimentary rock.
Exam tip
Learn the four pairs: sandstone–quartzite, limestone–marble, shale–slate, granite–gneiss.
Sources
- NCERT Class XI — Fundamentals of Physical Geography, chapter 'Minerals and Rocks'
- Arthur Holmes — Principles of Physical Geology, chapter on metamorphic rocks