The sulphuric acid process has the ability of treatment all types and grades of monazite sand economically in industrial scale, so it was chosen for this study to digest the Egyptian monazite sand concentrate of assaying 48.5% purity and grain size of -100 mesh. The results of digestion experiments that verify the maximum digestion efficiency of monazite sand which reaches (93.7%) were obtained at temperature of 220°C, acid/monazite ratio of 1.6/1, digestion time of 2.5 hrs and acid concentration of 93%. The related extraction efficiency of rare earths was 93.3%. Separation of rare earths by precipitation from the resultant clear sulfate solution after leaching, decantation and filtration was carried out using ammonium hydroxide (17.5%). The results of these experiments reveal that the dilution ratio of 17.5/1 (parts of water to one part of the original digested monazite sand weight) verifies efficient separation. At this dilution ratio the precipitation efficiency of rare earths was 98.2% at pH 3.3.