Mineralogy of drill cores from Jabal Sa'id, Kingdom of Saudi Arabia

Abstract

The mineralogy of three drill cores from the apogranite at Jabal Sa'id was determined principally to identify those minerals containing rare earths, niobium, tantalum, thorium, zirconium, and tin. Heavy mineral studies of two other drill cores indicate that the deposit is enriched in rare earths. The principal rare earth minerals are bastnaesite and doverite; other rare earth minerals include monazite and synchisite. Niobium occurs in pyrochlore; zirconium is present in zircon. Thorium is found principally in thorite and secondarily in thorianite. Autoradiographs show the distribution and relative sizes of several radioactive minerals. Microprobe studies of grains of eight different minerals indicated that significant elemental substitution took place in most of them. The rare earth metals cerium and lanthanum occur in significant amounts in pyrochlore; yttrium is abundant in doverite and is also present in bastnaesite, thorite, and zircon. Niobium substitutes for titanium in anatase and brookite, and some tantalum occurs with the niobium in pyrochlore. Minor amounts of thorium are found in bastnaesite, doverite, and zircon. Small amounts of uranium mostly occur with the thorium in thorite. Tin minerals were not found in any of the samples, but small and variable amounts of this element occur in bastnaesite, doverite, hematite, and zircon. The potential ore minerals in the apogranite commonly occur along the grain boundaries of the larger quartz and feldspar. Most of the ore minerals have diameters in the range 0.020 to 0.20 mm.