1. OPTICAL MINERALOGY TRIVIA ROUND 2!

2. Round 2 – Question 1 Under cross-polars, when will this mineral go to extinction?

3. Round 2 – Question 2 The interference colors shown by a mineral under cross-polars depends on the thickness of the mineral and what else?

4. Round 2 – Question 3 When a mineral shows nearly black interference colors, what type of indicatrix section is in the plane of the mineral?

5. Round 2 – Question 4 What type of optic figure is this?

6. Round 2 – Question 5 What causes the black isogyres

7. Round 2 – Question 6 What is the optic sign indicated by this figure?

8. Round 2 – Question 7 Which two vibration directions in this biaxial indicatrix will display maximum birefringence?

9. Round 2 – Question 8 This is an example of a negative biaxial indicatrix. What is does this imply about the relative values of ,  and  ?

10. Round 2 – Question 9 What type of optic figure is this?

11. Round 2 – Question 10 If the colors go up in figure C, what does this imply about the sign of elongation?

12. End of Round 2 Pass your answers to the team on your right for grading.

13. Round 2 – Question 1 Under cross-polars, when will this mineral go to extinction? When the O & E vibration directions are parallel to the polarizing directions (N-S/E-W)

14. Round 2 – Question 2 The interference colors shown by a mineral under cross-polars depends on the thickness of the mineral and what else? birefringence or difference in two indicies of refraction in section

15. Round 2 – Question 3 When a mineral shows nearly black interference colors, what type of indicatrix section is in the plane of the mineral? circular section

16. Round 2 – Question 4 What type of optic figure is this? uniaxial optic axis figure

17. Round 2 – Question 5 What causes the black isogyres Alignment of two vibration directions parallel to polarizers

18. Round 2 – Question 6 What is the optic sign indicated by this figure? Positive

19. Round 2 – Question 7 Which two vibration directions in this biaxial indicatrix will display maximum birefringence?  and 

20. Round 2 – Question 8 This is an example of a negative biaxial indicatrix. What is does this imply about the relative values of ,  and  ?  is closer to  than to 

21. Round 2 – Question 9 What type of optic figure is this? Acute Bisectrix (Bxa)

22. Round 2 – Question 10 If the colors go up in figure C, what does this imply about the sign of elongation? Length slow