Alumina added with Mn3O4 up to 7.5 cat% of Mn was prepared by conventional ceramic processing, and the sintering behavior and the optical properties of which were studied as functions of Mn content. Densification and grain growth of alumina were enhanced by Mn addition up to 0.75 cat% but was leveled off at higher concentrations. XRD revealed that Al2MnO4(galaxite) was formed as a second phase in the specimens with more than 0.75 cat% of Mn. Thus it is believed that either the solid solution effect of Mn or the Zener effect of Al2MnO4 becomes predominant in the sintering of Mn-added Al2O3 according to the additive concentration. UV-VIS reflectivity(SCI) spectra of Mn-added Al2O3 consisted of smooth bottoms in 300~550 nm wavelength range and plateaus at wavelengths longer than 650 nm. The reflectivity spectrum continuously moved downward, and the specimen color became darker and thicker with increasing Mn content. The CIELAB color change with respect to standard white was also dependent on the amount of Mn added: TRIANGLE L^{*} (D65) negatively increased and TRIANGLE E _{ab} ^{*} (D65) positively increased with increasing Mn content, probably due to Mn substitution to Al and/or the mixing effect of black Al2MnO4 as a second phase.
