Petrography and Geochemistry of Gahirat Marble in Relation to Geotechnical Investigation: Implications for Dimension Stone, Chitral, Northwest Pakistan

The modernization of human civilization has led to the prospect of better and more durable building materials. Marble, found in various colors and textures, has been used as a building stone for centuries, either as cut stone or polished stone. The present study evaluated the petrological, geochemical, and geotechnical characterizations of the Gahirat Marble formation as a building stone. It is exposed over an area of 160 square kilometers in southwestern Chitral. The Gahirat Marble formation has been divided into two parts, i.e., the eastern and western parts. The eastern part is a coarse crystalline rock that exhibits a granulose structure and was subjected to amphibolite facies metamorphism, whereas its western part is a coarse-to-medium crystalline rock that displays a differential granulose structure and was subjected to green schist facies metamorphism. Petrographically, it is composed mainly of calcite (>92%) with minute quartz, chlorite, muscovite, biotite, garnet, and opaque minerals. The X-ray fluorescence (XRF) technique was used to analyze the chemical composition of the Gahirat Marble showing that it is a pure calciocarbonate marble (CaO: 53.16–55.02 wt.%). The specific gravity measured varies from 2.46–2.71 gm/cm3, water absorption is <0.2%, sulfate soundness is <0.65, and due to its unconfined compressive strength, it is classified as strong rock, thus conforming to ASTM C503 specifications. The results acquired from the investigated samples suggest they are suitable as dimension stones. Until now, it has been limitedly mined and marketed but can be further exploited for export trade, based upon its petrographic, geotechnical, and geochemical characterization.