Computational Geology 19 Classification and the Combination of Sets

Introduction The special issue of this journal (Nov. 2000) that was devoted to “Some Great Ideas for Geoscience Courses,” included nine ideas under the heading “Earth materials.” Six of those papers involved classification (Thomas and Thomas, 2000; Dowse, 2000; Reynolds and Semken, 2000; Harper, 2000; Christman, 2000; Niemitz, 2000). Classification of rocks and minerals is obviously a necessary component of introductory geology courses. Classification of rocks and minerals is taught in geology courses in order to understand geology better and to provide a basis for communication. Classification of rocks and minerals also provides a rich illustration of mathematical concepts involved in classification in general. These concepts, which are staples of courses in logic, occur in the mathematics curriculum in courses on discrete mathematics. This column is the second on the connection between sets and geological terminology. The context for the first (CG-18) was planets and moons. The context for this one is rocks.