1.
Match the minerals in Column 1 to their characteristic optical properties in Column 2.
| Column 1 | Column 2 |
|---|---|
| P. Zircon | i. Pink to green pleochroism |
| Q. Orthopyroxene | ii. Very high positive relief |
| R. Muscovite | iii. Cyclic twinning |
| S. Cordierite | iv. Third order birefringence |
Exam Year(s)
IIT JAM - 2026,
Answer: C
The correct matching is P-ii; Q-i; R-iv; S-iii.
- Zircon has refractive indices near 1.92 to 1.98, far above the mounting medium, so it shows very high positive relief (ii).
- Orthopyroxene (hypersthene) shows characteristic pink to green pleochroism (i).
- Muscovite has a birefringence of about 0.036 to 0.049, giving bright upper second to third order interference colours (iv).
- Cordierite forms cyclic (sector) twins that divide a grain into three or six segments (iii).
Options giving muscovite the cyclic twinning, or zircon the pleochroism, swap properties that belong to cordierite and orthopyroxene.
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