Birefringence of Rock-forming Minerals

Question 1

Quartz

Answer 1

Birefringence: 0.009 | Interference Colors: First-order gray to yellow

Question 2

Plagioclase Feldspar

Answer 2

Birefringence: 0.007 - 0.013 | Interference Colors: First-order grays to yellows

Question 3

K-Feldspar (Orthoclase, Microcline)

Answer 3

Birefringence: 0.005 - 0.008 | Interference Colors: First-order grays

Question 4

Muscovite

Answer 4

Birefringence: 0.036 - 0.049 | Interference Colors: Third-order interference colors

Question 5

Biotite

Answer 5

Birefringence: 0.020 - 0.070 | Interference Colors: Third-order, often brownish

Question 6

Olivine

Answer 6

Birefringence: 0.035 - 0.052 | Interference Colors: Third-order interference colors

Question 7

Pyroxene (Augite)

Answer 7

Birefringence: 0.018 - 0.034 | Interference Colors: First- to second-order

Question 8

Amphibole (Hornblende)

Answer 8

Birefringence: 0.020 - 0.030 | Interference Colors: First- to second-order

Question 9

Garnet

Answer 9

Birefringence: None (Isotropic) | Interference Colors: No birefringence

Question 10

Calcite

Answer 10

Birefringence: 0.154 - 0.174 | Interference Colors: High-order interference colors

Question 11

Dolomite

Answer 11

Birefringence: 0.179 | Interference Colors: High-order interference colors

Question 12

Zircon

Answer 12

Birefringence: 0.038 - 0.065 | Interference Colors: High-order interference colors