Discussion

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

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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