Review Questions for Lecture 14: Earth's Crust
                Tectosilicates I.

1. Why is 75% of the Earth's crust composed of tectosilicates?
2. Olivine occurs in mafic and ultramafic rocks, whereas quartz
    occurs in felsic or silic rocks. Why?

3.   Draw a radial cross section of the Earth, labeling the major
    minerals or element in each subdivision, and the approximate
    depth of each subdivision.

4.  What is the primary building block of a tectosilicate?

5. Quartz is chemically simple but structurally complex. Name
    two high pressure forms and two high temperature forms.
    Based on the P-T of their formation, which would have the
    closest packing?

   If you find coesite in your rock, what would it tell you about
    the conditions in which your rock formed?

    Why do you not find alpha and beta quartz together in  your rock?

6. Why is opal referred to as a "Mineraloid"?
    (What is a mineraloid?)