We have undertaken a comparative study of the seismic properties of an anorthosite. The seismic properties have been calculated from the lattice preferred orientation (LPO) of plagioclase (90% by volume) and olivine (10% by volume), and the elastic constants of these minarals. Laboratory measurements of Vp (24 directions) and Vs (6 directions) have been made on the same sample at room temperature and pressures up to 1.0 GPa. The two techniques agree to within 0.1 km/s for all orientations studied when the Voigt averaging method is used. Hill and Reuss averaging methods give calculated velocities significantly lower than the experimental ones. A study of the difference between the velocity values given by the two methods reveals a systematically larger departure in orientations normal to the foliation. The orientation dependent difference between the two techniques can be explained if there are small error in the elastic constants for single crystal plagioclase used in the initial calculations. The axial LPO symmetry of the plagioclase with all the crystallographic b axes parallel to the specimen symmetry axis allowed us to calculate C22 (normal to (010) directly from the laboratory measurments of Vp. Some constraints can be put on C22, C44, C66, C12 and C23. On average our data required 10% modification of the single crystal constants reported by Ryzhova (1964). ¿American Geophysical Union 1993