CSIR NET June 2016 Q76: Petrology & Mineralogy
Common optical mineralogy properties used for mineral identification under the petrographic microscope include relief/extinction style, twin type, and interference colour behaviour.
Epidote is known for its patchy/mottled anomalous interference colours (R); kyanite shows high relief with inclined extinction (P); nepheline typically shows straight extinction as a low-relief, uniaxial mineral (S); sanidine (an alkali feldspar) characteristically shows Carlsbad twinning (Q). This gives A-R, B-P, C-S, D-Q. Option 3 is correct.
1), 2), 4) Incorrect — these permutations mismatch minerals with properties inconsistent with their well-known optical behaviour (e.g., assigning Carlsbad twinning, a feldspar twin type, to kyanite or epidote is inconsistent with standard optical mineralogy). 3) Correct — matches each mineral's diagnostic optical property as established in standard petrography.