The Problem 11 placemark takes you to the Illinois Fluorite District near Cave-in-Rock, IL, which once was responsible for more than 50% of total US fluorite production (now all fluorite is imported into the United States). Fluorite (CaF2) forms as cubic crystals, but when broken, it exhibits cleavage that forms triangular luster faces that look like two pyramids stacked on top of each other. How many directions of cleavage does fluorite exhibit (see animation in placemark)?