Of all of the surprises I had as a geology undergrad, I would rank the beauty and information content of looking at thin sections of rock under cross-polarized light in the top five or so. Really, really spectacular, especially mafic igneous rocks (those with high Mg, Fe +/- Ca such as basalts and gabbros), metamorphic rocks, and even limestones. The range and vibrancy of the interference colors is breathtaking, and seeing things like halos of radiation damage around zircons (high U and Th content) was a bit shocking.<p>I'd like to recommend folks to take a look if they get a chance, but really, I have no idea when anyone would get that chance. Petrographic microscopes are expensive and I don't think universities would be that cool with hordes of outsiders oohing and aahhing in the labs. Did anyone get to do this in high school?