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5 Define the essential properties of each of the seven (if hexagonal and trigonal are separated) crystal systems in terms of the properties of their Bravais lattices and their crystallographic axes (lengths and intersection angles).

6 6 In Weiss parameters and Miller indices, what do the three sequential parameters or indices represent? Convert the following Weiss parameters into the equivalent Miller indices.2, ∞, 1½, 1, 22, ∞, 2, 2, 11/3, , 1

7 Explain the meaning of the following Miller indices in terms of crystallographic axial intercepts with respect to axial ratios(111){111}(1 2){hkl}(hh )

8 What are twinned crystals and what are their chief defining characteristics? What is the essential difference between contact and penetration twins? Give a couple of good examples of each.

9 What are polymorphs? What is the difference between reconstructive and displacive polymorphs? Give an example or two of each. Which is most likely to produce long term metastable polymorphs?

1 Davis, G.H., Reynolds, S.J., and Kluth, C.F. (2011). Structural Geology of Rocks and Regions, 3e. New York: Wiley 864 pp.