Sodium Plagioclase Calcium Plagioclase Phaneritic Granite Diorite Gabbro Aphanitic Rhyolite Andesite Basalt Geoscientists at the University of British Columbia has prepared a nice figure which summarizes information about the Classification of Igneous Rocks . Take a look at their companion piece on the Rock Cycle . Note that a granite is the coarse grained equivalent of a rhyolite. That is, if the rate of cooling is very slow a granite will form. The same melt, cooled rapidly, will form a rhyolite.
Most departments have rock and mineral display cases.
Spend sometime looking at igneous rocks. Describe their textures and see if you can determine the major minerals present. Buildings are often constructed from polished rock slabs and good field trips to local buidlings can often be arranged.