Kaolinite

I've been building mineral models out of ping pong balls. The clay mineral structure is composed of Silicon-Oxygen tetrahedrons (white) and Aluminum-Oxygen octahedrons (orange). There is one relatively minor difference between this model and an actual clay mineral (besides the chemical composition and size, of course).

I need to figure out how I can demonstrate cation exchange... perhaps I can stick small magnets on some of them...