Classroom Index-Card Simulations of Crystal Growth

Using colored index cards as the “building blocks” of two-dimensional “crystals,” students assemble crystals under several sets of instructordesignated conditions of time and geometry. After each simulation, the size and the number of crystals of different sizes are tallied. When all simulations are complete, data from the multiple simulations are compared. At the simplest level, results can be interpreted in terms of coolingor quenching-time/crystal-size relations commonly introduced in introductory geology. At a higher level, the different conditions of the simulations are examined as analogs for transport and reaction processes operating during crystal growth. Once the basic processes have been illustrated (by analogy) and classified, a framework has been established within which instructors can examine individual transport and reaction processes in more detail.