Eight sediment cores from deep-water environments in the Red Sea have been examined. Carbonate minerals are dominant in each of the four lithologic facies identified in the cores. The most widely developed facies is mineralogically characterized by the presence of high- and low-magnesian calcite, with aragonite subordinate or absent. Hard layers interbedded with light and dark lutites contain aragonite which, upon precipitation under conditions of high salinity and temperature, bound the grains together and provided drusy fibrous infilling and syntaxial fibrous growth on grains. The aragonite is subject to dissolution upon return to normal salinity and temperature conditions. Dark lutites represent deposition of materials under reducing conditions. The facies characterized by the presence of reef-derived debris is rich in aragonite and mineralogically similar to reef-associated shallow-water skeletal sands of the Bahamas.