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Updated: 1 Sep 2000
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2 Determine point group symmetry for blocks having various decorations on their sides - examples attached (cf. K., p. 20).
3. Determine point group symmetry for external morphology of wooden crystal models (cf. K., p. 20-27, examples in exercise 2) - this determines the crystal class as well.
4. Discuss (list) the crystal systems and their distinctions in terms of symmetry. What is their relation to point groups, space groups, or Bravais lattices (see definitions, below)? How are these different classification tools used in developing a systematic concept of mineralogy?
5. Be familiar with the relationship of Hermann-Mauguin symbols to coordinate axes in crystals - know the hierarchical system by which the symbol elements are assigned (cf. K., p. 35).
6. Be familiar with the concept of Miller indices (K. p. 53-60) and be able to index relatively simple crystal forms (cf. K., exercises 2 and 3 for practice examples).
7. Given a representative space group symbol, be able to specify the crystal system, define the symmetry operators present, and discuss the their relation to the crystal axes and to each other.
8. Given simple crystal structure diagrams (e.g., K. Ex 13), discuss the various symmetry operators present (rot- and screw-axes, mirrors, glides), show their locations, and give the space group symbol consistent with these operators - see diopside (K., p. 211) or sanidine (K., p. 209) structure diagrams.
9. Derive Braggs law for x-ray diffraction (XRD). Discuss how it enables determination of d-spacings within mineral structures.
10. The following XRD methods are described in KH (pp. 279-288): Laue method, rotation method, Debye-Scherrer camera method, powder diffractometer method. Given certain types of mineral material (small well-formed single crystal, massive lump of poorly formed mineral, mineral with highly-developed basal cleavage such as mica), what kind of data results from each of these methods? What are the advantages or disadvantages of each? (K. Ex 14, 15).
11.The concepts of electrostatic (ionic) bonding and ionic radii are widely used to describe structures of minerals (especially the silicates) (KH Ch. 4). What factors control/affect the magnitude of ionic radii?
12. How do effective ionic radii change with atomic structure or with P, T, coordination, ionic charge, structural site, etc.? Explain in general terms of atomic structure (KH Ch. 4). Provide mineral examples for these concepts.
13. What other types of bonding are represented in silicate minerals? Give mineral examples and especially relate to specific parts of the crystal structures (e.g., amphiboles, micas, clay minerals).
14. For the other mineral groups we have covered in the lab, what is the prevailing style of bonding (cf. KH, Ch. 4, 10, 11, etc.)? Again consider mixed bonding types. Refer to Table 4.11 (KH, p. 208) concerning bonding types. (e.g., native elements, oxides, hydroxides, halides, etc.)
15. Discuss compositional variations (e.g., between end members) and describe substitutions of the major cations in the following mineral groups :
(you should be generally familiar with all of these examples and know the end-member chemical formuli).
16. Select the components that best describe the compositional systems containing the above minerals, aluminosilicates, silica minerals, and/or carbonates and plot their end member compositions on simplified binary, ternary, or quaternary projections (molar basis). Note that the system required (and the components too) will depend on which mineral groups you choose to consider.
17. Discuss the structural classification system for silicate minerals (based on combinations of [SiO4]-4 tetrahedra); list the subgroups and give at least one mineral example (with chemical formula) for each (cf. KH, p. 214-216, Ch. 13).
18. Precisely, what is a solid solution? Discuss the three main types of solid solution and provide mineral examples for each (KH, pp. 233-236):
19. Describe substitutional solid solutions in terms of structural, P, T effects. This is best done for a specific mineral group (e.g., plagioclases, pyroxenes, olivines). Explain immiscibility and when/why it occurs - again with respect to specific minerals (cf. KH, ch. 4, 5, & 13).
20. Explain how temperature and crystal structure affect solid solutions of (a) pyroxenes, and (b) alkali feldspars (cf. KH, pp. 236-240; 321, 325-326). Give some details as to why exsolution occurs and how and why the coexisting phases vary in composition along the solvus curve as temperature decreases. Use the relevant phase diagrams to illustrate. Describe what the crystalline material will look like, texturally speaking.
21. Explain the "phase rule" and be prepared to apply it to simple phase diagrams, such as that for the aluminosilicates (andalusite, sillimanite, kyanite)or silica (a-b quartz, cristobalite, tridymite, etc.). What do the terms bivariant, univariant, and invariant mean (again relate these to a simple phase diagram)? (KH, ch. 9)
22. What is the effect of pressure and temperature on Gibbs free energy (G)? How do responses of G to P, T affect mineral stabilities? (KH, ch. 9)
23. What are "mineral facies" diagrams and how are they affected by changing P, T, bulk composition? (KH, ch. 9)
24. Discuss how mineral physical properties may be determined or controlled by crystal structure and/or chemical composition; give specific mineral examples for each (KH, ch. 4):
25. Definition of terms - you should develop good precise definitions of the following:
I suggest you prepare brief discussions/answers to the above questions and develop precise definitions for the terms listed above. The most efficient approach might be to split up the questions among yourselves to provide frameworks that you can share and embellish individually. This should not be as formidable as appears, as we have been emphasizing the above topics throughout the semester.
For the Crystallography Exam, I will prepare specific questions from this material (and may take some of them more or less directly). Questions likely will involve application of concepts or principles rather than request simple recitation of facts. The crystallography exam will include some definitions and at least five questions taken from above.