Geo-mechanical properties of marble deposits from the Nikani Ghar and nowshera formations of the Lesser Himalaya, Northern Pakistan - A review

Calcite and dolomite marble deposits from the Lesser Himalaya (northern Pakistan) have been investigated in the past; however, those studies were limited mostly to general geology. Increased domestic and international demands for marble necessitate precise quantitative analyses and characterization of these deposits consistent with international standards. This paper presents a review of the available literature and newly acquired information with emphasis on the geological data and interpretations thereof with respect to the occurrence, character and variability in minero-petrographic, geochemical and geotechnical characteristics of marble deposits of the Nikani Ghar and Nowshera formations. The variability within the deposits was found to be a function of 1) the concentration and distribution of minerals other than the main constituent calcite (i.e. dolomite, quartz, muscovite, mica, pyrite, apatite, K-feldspar, Fe₂O₃, TiO₂ and MgO), 2) the calcite grain size, texture and crystallinity, and 3) the physical and mechanical properties. The water absorption values for both the Nikani Ghar and Nowshera Formation marbles were lower than the internationally accepted ASTM standards.Astraight-line relationship was observed between the porosity, water absorption and calcite maximum grain size for the varieties investigated in the present study. The observed differences in the compressive as well as tensile strengths of these marbles may be due to variation in crystal structure, micro-cracking and/or the influence of secondary hydrothermal phase(s). The physical properties of the investigated 22 commercial marble varieties were consistent with the international standards for structural and decoration purposes. However, the presence of impurities renders these unsuitable for ground calcium carbonate production, cosmetic and medical use.