All of our specimens were blue, pale red, or red violet and contained less Fe and Ti than brown dumortierites reported in the literature. Optical properties are linearly related to minor-element composition, such that refractive indices and birefringence increase with increasing transition-metal concentrations, but decrease as the proportion of Fe to Ti increases. Optic axial angle varies in exactly the opposite way. Color and pleochroism (blue or pale red with E∥c, and colorless with E⊥c) in these dumortierites are attributed to charge transfer among Fe2+, Fe3+, and Ti4+ replacing Al in the Al(1) face-sharing octahedral chains. It appears from the correlation between color and composition that the blue color can be attributed to Fe2+-Fe3+ charge transfer, and the pale red to Fe2+-Ti4+ charge transfer. The Fe:Ti ratio 1:4 separates pale-red dumortierites (poorer in Fe) from blue ones (richer in Fe).