Study of Natural Marble Specifications in Southern Libya

Abstract

This study evaluates the chemical, physical, and mechanical specifications of natural ornamental stones from five quarry sites in the Wadi Alshatti / Zella region of southern Libya: Tarouth, Mahruqa Right, Mahruqa Left, Zella, and Al-Ghaylaniya, all locally marketed as "marble." Samples were characterized by X-ray Fluorescence (XRF) chemical analysis, bulk density and water absorption (ASTM C97), uniaxial compressive strength (ASTM C170), and sulfuric-acid (H2SO4) resistance, with three replicate specimens per site. Results show that Mahruqa Left exhibits the highest compressive strength (87.45 ± 0.77 MPa) and CaO content (87.8%), with low water absorption (0.31%) and a density of 2.68 g/cm3, consistent with a high-purity calcitic marble. Tarouth (CaO = 79.7%; 64.93 MPa) and Mahruqa Right (CaO = 75.9%; 64.00 MPa, currently inactive) classify as dolomitic and calcite-dolomite marbles, respectively. Chemical analysis reveals that the Zella stone is not true marble: its exceptionally high sulfate content (SO3 = 31.91%) identifies it as a calcite-sulfate onyx of evaporitic/hydrothermal origin rather than a metamorphic carbonate rock. Similarly, Al-Ghaylaniya, with MgO = 19.60%, the highest water absorption (8.78%) and the lowest compressive strength (34.30 MPa), is geologically a dolomitic travertine. These findings indicate that two of the five commercially traded "marble" sources are mineralogically distinct stone types, with direct implications for correct classification, pricing, and end-use selection in the Libyan dimension-stone industry.