Review Questions for Lecture 18:  Earth's Crust;

1. What is the linkage of the silicate tetrahedra in cyclosilicates?

2.  Can color be used as an identifying tool for beryl? tourmaline? corderite?
    If not, why not, if so, why?

3. What are the geologic environments/conditions, e.g. P, T, or composition, indicated by:

4. Why is tourmaline a good petrogenetic indicator?

5. What is piezoelectric? pyroelectric?
    What symmetry element must be absent for this to occur in a mineral?