Petrology is much less about describing and much more about trying to comprehend and explain.
Phase equilibria among minerals, as they have been investigated and reported by others, are the backdrop to almost everything we do in this course. I particularly favor graphical approaches to exploring phase equilibrium in both igneous and metamorphic rocks, because they are such powerful visual tools in helping us to understand chemical variations within minerals, chemical variations among rocks, and the structures and textures we see in rocks. Students are coached through the detailed petrographic examination of two rock suites, and present their results in symposia and formal papers. But, beyond careful description and interpretation this is also a course for imagining - particularly for imagining geologic histories. Since most of our students take both Petrography and Petrology, and in successive years, I am able to take each student to two different field areas.