The Impact of Mineralogical Characteristics on the Physicomechanical Properties of Serpentinite from Prang Ghar, Mohmand District, Pakistan

Abstract

The serpentinite samples of the Prang Ghar Mohmand Agency were analysed petrographically and
physicomechanically to assess their potential as dimension stone and aggregate material. These rocks are
prominently exposed along the suture zone between the Indian Plate and the Kohistan Island Arc, known as the
Main Mantle Thrust Zone (MMTZ). On fresh surfaces, the serpentinite ranges in color from light green to dark
green, while weathered surfaces appear yellowish green. Petrographically, the serpentinite is fine- to medium
grained and consists of serpentine, actinolite, talc, and magnesite, along with ore minerals like magnetite and
chromite in varying amounts. The serpentinite can be categorized into four types: serpentinite, talc-serpentinite,
actinolite-serpentinite, and chromite-bearing serpentinite. The physicomechanical properties were assessed
through a series of tests, which were then compared to ASTM standards to evaluate their quality. These tests
included unconfined compressive strength (UCS) (46.0–49.94 MPa), cube test (198.56–234.34 MPa), flexural
test (8.20–13.28 MPa), specific gravity (2.58 mg/cm³), and soundness (3.35%). The results indicate that the
serpentinite exhibits properties that meet international standards for use as dimension stone and coarse
aggregate. Based on these findings, it can be concluded that the Prang Ghar serpentinite is a viable material for
construction applications, such as flooring and exterior wall cladding. This study emphasizes the strong
correlation between the mineral composition of serpentinite and their physicomechanical properties. An increase
in talc content is associated with reduced strength, along with higher water absorption and porosity.
Additionally, the presence of actinolite and ore minerals also influences the physicomechanical behavior of
serpentinite. This study confirms the necessity of petrographic analysis before using rock as an engineering
material.

Keywords: Dimension stone, Prang Ghar, serpentinite, petrography, physicomechanical properties.