1. CRYSTALLOGRAPHY TRIVIA FINAL ROUND!

2. Round 3 – Question 1 Twins are said to add another level of symmetry to a crystal. Why is this?

3. Round 3 – Question 2 Which of the following statements about twins are true? - penetration twins form by reflective symmetry across a mirror plane - the composition plane of contact twins corresponds to a mirror plane - polysynthetic twins form from variably oriented mirror planes

4. Round 3 – Question 3 The smallest unit of lattice points that define the basic ordering of atoms in a mineral is called what?

5. Round 3 – Question 4 Which of these 2-D lattice nets is not primitive?

6. Round 3 – Question 5 Besides translation, what other symmetry element is possible in 2D lattices that is not present in point group symmetry of single crystals?

7. Round 3 – Question 6 These 3D unit cell types are possible in what crystal class?

8. Round 3 – Question 7 Screw axes combine what two symmetry operations?

9. Round 3 – Question 8 Which image is an example of a right- handed screw axis?

10. Round 3 – Question 9 P6 3 /m2/c2/m The space group - P6 3 /m2/c2/m belongs to what crystal system?

11. Round 3 – Question 10 What is the maximum possible number of symmetry combinations that define 3D lattice arrays?

12. Extra Credit Question Choose the number of points you wish to wager What unit cell type and symmetry operations are present in the space group: I4 1 /a2/m2/d and what crystal system does it belong to?

13. Round 3 – Question 1 Twins are said to add another level of symmetry to a crystal. Why is this? Twin symmetry elements do not usually correspond to crystal symmetry elements

14. Round 3 – Question 2 Which of the following statements about twins are true? - penetration twins form by reflective symmetry across a mirror plane - the composition plane of contact twins corresponds to a mirror plane - polysynthetic twins form from variably oriented mirror planes

15. Round 3 – Question 3 The smallest unit of lattice points that define the basic ordering of atoms in a mineral is called what? A Unit Cell

16. Round 3 – Question 4 Which of these 2-D lattice nets is not primitive?

17. Round 3 – Question 5 Besides translation, what other symmetry element is possible in 2D lattices that is not present in point group symmetry of single crystals? Glide Lines

18. Round 3 – Question 6 These 3D unit cell types are possible in what crystal class? Orthorhombic

19. Round 3 – Question 7 Screw axes combine what two symmetry operations? Rotation and Translation

20. Round 3 – Question 8 Which image is an example of a right- handed screw axis?

21. Round 3 – Question 9 P6 3 /m2/c2/m The space group - P6 3 /m2/c2/m belongs to what crystal system?Hexagonal

22. Round 3 – Question 10 What is the maximum possible number of symmetry combinations that define 3D lattice arrays?230

23. Extra Credit Question What unit cell type and symmetry operations are present in the space group: I4 1 /a2/m2/d and what crystal system does it belong to? Unit Cell: Body-centered Symmetry Operations: 4-fold screw axis with a perpendicular glide plane with translation in the a direction 2-fold rotation axis with a perpendicular mirror plane 2-fold rotation axis with a perpendicular diamond glide plane Crystal System: Tetragonal

24. And the winners are...