Classification of black decorative stones from Warangal District, Andhra Pradesh, India

Despite abundant usage of Indian black decorative stones, no systematic approach has been made to study their properties. In this paper an attempt has been made to study the geoparametrical and geotechnical properties of the stones from ten active quarries in the Dornakal-Balpao-Venkatayapalem, Warangal district, Andhra Pradesh, India, including colour, hardness, texture, grain size, composition, macro- and micro-joints, specific gravity, dry density, moisture content, water absorption, porosity, uniaxial compressive strength (compressive strength), tensile strength, shear strength, rebound hardness number, point load strength index and rock hardness. Regression analyses were undertaken; the correlation coefficient obtained from ranged from 0.80–0.96. On the basis of these results, a new classification system for black decorative stone is proposed with four classes ranging from I (very good) to IV (poor). It is appreciated that the classification is based on limited data but it provides an important advance with implications for improving the present ad hoc, often wasteful quarrying philosophy in India.