Optical anomalies in crystals are puzzles that collectively constituted the greatest unsolved problems in crystallography in the 19th Century. The most common anomaly is a discrepancy between a crystal’s symmetry as determined by its shape or by X-ray analysis, and that determined by monitoring the polarization state of traversing light. These discrepancies were perceived as a great impediment to the development of the sciences of crystals on the basis of Curie’s Symmetry Principle, the grand organizing idea in the physical sciences to emerge in the latter half of the 19th Century. Optically Anomalous Crystals begins with an historical introduction covering the contributions of Brewster, Biot, Mallard, Brauns, Tamman, and many other distinguished crystallographers. From this follows a tutorial in crystal optics. Further chapters discuss the two main mechanisms of optical dissymmetry: 1. the piezo-optic effect, and 2. the kinetic ordering of atoms. The text then tackles complex, inhomogeneous crystals, and the complex optical properties resulting from the superposition of anomalies having various etiologies. The book treats the literature comprehensively, but uses illustrations from the authors’ laboratories as the subjects of detailed analyses. This is an invaluable text for crystallographers, mineralogists, and petrologists interested in the growth of minerals and synthetic crystals, and their optical properties. It is also ideally suited to students of optical mineralogy, professional scientists and engineers as well as historians of science.