ENVIRONMENTAL FACTORS INFLUENCING TEXTURAL PATTERN AND MINERALOGICAL COMPOSITION OF COASTAL BEACH SEDIMENTS OF RAS EL BEHAR - RAS GEMSA AREA AND ADJACENT ISLANDS, NORTHERN RED SEA, EGYPT. AHMED A. REFAAT and MAHMOUD A. M. AREF Geology Department, Faculty of Science, Cairo University, Giza, Egypt The beach sediments of the northern part of the Red Sea coast (Ras El Behar - Ras Gemsa) and adjacent islands (Um el Heimat el Kebira, Um el Heimat el Saghira, North Gaysum, South Gaysum and Ghanim) have been studied for their textural pattern and mineralogical composition. The resultant data on texture and mineral composition have been interpreted in the light of the coast morphology and environmental factors such as wind, waves and currents. The mean grain size of the beach sediments is at maximum (gravel and coarse sand) at the tip of the headlands and the seaward side of the islands, which decreases to fine sand at the coast embayments and the shoreward side of the islands. The beach sediments at the tip of the headlands and the seaward side of the islands are poorly sorted and negatively skewed due to the high-energy condition of waves and currents. Whereas the beach sediments at the coastal embayments and shoreward side of the islands are moderately well sorted and positively skewed due to the low-energy condition of waves and currents in sheltered zones. The beach sediments of the Red Sea coast are composed of siliciclastics as well as carbonate debris, whereas the beach sediments of the islands are dominated with calcareous and aragonitic shell fragments with fewer amounts of siliciclastics. Opaque minerals are greatest at the Red Sea coast especially at Gemsa Bay reaching a maximum of 88 %, and smallest at the islands reaching 42 %. The opaques and ultra-stable minerals are significantly concentrated in areas of embayments where fine sand beaches predominate. On the other hand, areas of erosion (headlands and seaward side of the islands) are relatively less abundant in these minerals. The observed variations in texture and heavy mineral concentrations within beach sediments of the Red Sea coast and islands are the product of selective sorting by waves and longshore currents of sediments derived from the adjacent rocks at Gebel El Zeit, Esh El Mellaha Range, Ras Gemsa and coral reefs. These variations could be successfully used in order to discriminate between shoreward and seaward sides of the Red Sea islands and between sheltered and open coasts.