To supply the growing demand for kaolinitic clay for the ceramic, refractory, and filler industries in the Saudi local market, the SGS Industrial Minerals Section was encouraged to carry out an exploration program through the 100-km long Wasia Formation outcrops in the south Jabal Shahbah area, southeast of Al Kharj, between 2001 and 2002. The outcrops extend from south Jabal Shahbah, some 70 km southeast of Al Kharj, to an area just northeast of Layla, approximately 150 km southeast of Al Kharj. The objective of the project was to locate deposits of kaolinitic clay with potential as a mineable and/or economic resource, in terms of quality and tonnage. Previous studies indicated the presence of kaolinitic clay deposits in the vicinity of Al Kharj, particularly at Khushaym Radi, Jabal Shahbah, and close to the northern edge of the south Jabal Shahbah area. Deposits in these areas are believed to have a favorable economic potential for use in the ceramic industry. The lithostratigraphy of the kaolinitic clay-bearing Wasia Formation outcrops can be divided into two members: (a) an upper member, displaying bedded, non-fossiliferous sandstone with variegated (locally white) kaolinitic clay and rare limestone; and (b) a lower member, consisting of variegated kaolinitic clay, overlain mainly by thin beds of limestone associated with calcitic geodes. The exploration program included the collection of a total of 122 samples, consisting of 41 surface samples and 88 trench channel samples, which were subjected to chemical analyses (major oxides, CL); 41 samples used in a methylene blue adsorption test; 20 samples used in firing tests; 11 samples for qualitative X-ray diffractometry analyses; and 5 samples used in preliminary processing tests. Two types of clays were discovered, namely: Type 1, a pale kaolinitic clay found in the northeastern part of the exploration area, which forms a small lens; and Type 2, a variegated kaolinitic clay that forms discontinuous lenses, and is weakly exposed along a strip some 40 km long. The study area, based on its commercial potential, was divided into five lenses, numbered 1 through 5. Lens-1 corresponds to the Type-1 clay, and is a pale kaolinitic clay, white to off white, pale yellow in color, pisolitic, and assays 31 percent Al2O3, 48 percent SiO2, and 1.54 percent Fe2O3. The Lens-1 deposit is 1.7 m in average thickness and is estimated to contain 3 million tonnes. Lenses 2-5 corresponds to the Type-2 clay, which is the variegated kaolinitic clay. These lenses include most of the deposit, with assays of 60.30 percent SiO2, 20.3 percent Al2O3, and 2.8 percent Fe2O3. In these lenses the deposit averages 2.50 m in thickness with an average overburden of 0.84 m thick, containing resources of 79 Mt. Mineralogical examination by XRD yield kaolinite as the major proportion of the whole-rock samples indicating kaolinitic clay, and a variable amount of quartz and other associated trace minerals. The ceramic aptitude tests on raw trench samples from both types of clay yield good results for tile manufacture. Preliminary upgrading using the hydrocyclone process succeeded in concentrating alumina in Lens-1 from 31 percent to 33 percent, and decreasing soluble salts by washing the samples with 0.01 percent SO3, and 0.18 percent CL. These upgraded samples showed white to whitish-pink after testing, which indicates that the kaolinitic clay in these lenses (Lens-1 and 3) is suitable for sanitary ware use, although detailed testing has to be carried out to prove its suitability. The chemical composition of chamotte from the pale-colored kaolinitic clay in Lens-1 is 42.20 percent Al2O3. Chamotte manufactured from this clay can be suitable for high-alumina refractories by adding a small amount of bauxite. The chemical compositions of both types of kaolinitic clay meet the required specification for Portland cement manufacture in terms of alumina, alkalis, and soluble salts. A pozzolanic activity test carried out partially on variegated kaolinitic clay samples after calcination at 700°C shows encouraging results for use in pozzolanic cement. The mining study includes industrial indicators of kaolin in ceramics and refractory industries; market study of kaolin; the Kingdom’s production, imports and exports; estimation of the project’s production capacity; method of mining, the required equipment for implementation of the project, manpower, project life, total cost, net profits, and the rate of annual revenue. The study shows that the Kingdom imported about 35,000t kaolin materials in 2004, as well as 468,154 of tiles and square tiles. Therefore the exploitation of the Jabal Shahbah deposit (Lens-1) will lessen the need for imported kaolin, whether as a raw material, or in the form of manufactured products. This study also assume an investment project, based on exploiting part of the Jabal Shahbah kaolin deposit to about 1 Mt throughout a period of ten years, will yield 23 percent as an Investment Rate of Return. It is recommended to carry out prefeasibility studies including core drilling, detailed lab tests, mining studies (including geostatistical studies), and precise reserves estimation.
Al Nakhebi, Z., Tayeb, O., Bayashoot, A., and Al Qurashi, M., with a section on mining studies by Al Malhi, M., Al Ahmadi, M., and Eskander, N., 2007, Exploration of kaolinitic clay deposits in the south Jabal Shahbah area, Kingdom of Saudi Arabia: Saudi Geological Survey Open-File Report SGS-OF-2006-4, 35 p., 24 tables, 20 figs., 4 apps.