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When teaching total internal reflection, fiber optics, and in particular fiber optic imaging, it is interesting to show that nature had this all figured out millions of years ago. A striking example is one form of the mineral Ulexite, hydrated sodium calcium borate hydroxide—NaCaB5O6(OH)6 · 5H2O.1 An acicular (i.e., composed of slender needle-like crystals) habit of Ulexite found primarily in California and Nevada2 consists of almost perfectly aligned, parallel, transparent fibers, shown Fig. 2. The structural arrangement of the fibers results in effective “cladding” of the individual fibers due to the lower index of refraction in the space between the fibers.3 Polished samples of Ulexite exhibit nearly perfect imaging properties along the fiber direction, as shown for the sphere in Fig. 1(a). When the sphere is rotated...