Abstract
The marble deposits at Jabal Farasan represent a part of a prominent nappe structure in the Rabigh quadrangle in western Saudi Arabia. The marble deposit occurs in beds interbedded with foliated rnetachert and mafic green schists. The marble and the associating rocks are of late Neoproterozoic age.
Based on XRD analyses and microscopic investigation, the present author was able to classify the Jabal Farasan marble into four major petrographic types as followS: pure white marble (slightly graphitic), graphitic marble, diopside marble and tremolite marble. Mineralogical and textural evidence suggest that the appearance of diopside depends on the availability of Mg in the limestone precursor prior to regional metamorphism, i.e. dolomitic limestone. Tremolite in most cases is confined to micro-shear planes characterized by relative increase in silica activity.
The physical properties, loss on ignition and brightness measurements of the Jabal Farasan marble deposits were determined to establish its suitability for end-product use. The loss on ignition values vary from low to high (10.61 wt% to 42.32 wt%). The internationally recommended loss on ignition (L.O.I.) value is around 40 wt%. Most Jabal Farasan samples have a low brightness parameter due to common presence of both crypto- and well-crystalline graphite. The white tremolite marble is the only type at Jabal Farasan that fulfils the specifications for use as filler in paper and other industries. The chemical analysis of end products shows that CaO content varies From 21.39 to 56 wt%. Other impurities are Fe2O3, Al2O3, MgO2 and SiO2. Only the contents of both MgO and SiO2 are higher than 1%.
The bulk samples have shown satisfactory properties (good strength, water absorption and bulk specific gravity Values) corresponding with the requirements of dimensional stones used in the building industry. Jabal Farasan marble deposits could provide the domestic market building industry but it might be difficult to Supply for the international market because of acute competition from other world deposits.