We have measured the infrared reflectance spectrum of the ordinary ray of a zircon single crystal in order to determine the optical constants of the E(u) modes. With the obtained data and the optical parameters corresponding to the A2u modes (extraordinary ray) taken from literature, we have analyzed the absorption spectra of zircon powders by using the Maxwell-Garnett Theory (MGT) and the Effective Medium Theory (EMT), which take into account the effects of the shape and aggregation state of the particles. This analysis showed that although MGT can account for the main vibrational zircon features, EMT seems a more appropriate approach to interpret the powder spectra since it gives a more accurate estimation of the particle aggregation effects. From the above study, the assignment of the bands in the infrared powder spectrum of 2ircon has also been carried out.