Igneous Rock Classification
and is replicated here as part of the SERC Pedagogic Service.
I give each small group of students about 25 igneous rock samples to examine. I ask them to organize the samples into groups and to be prepared to explain the reasoning behind their groupings. We then have a whole class discussion of the various classification schemes devised. Finally, I distribute the IUGS igneous rock classification scheme and we discuss its reasoning and use.