Blast optimisation studies were conducted at an opencast coal mine in India for selection of a site specific explosive for different rock types. This seismic refraction survey technique was applied at sandstone benches of a coal mine for rock mass characterisation and blast optimisation by impedance matching of explosives. Field experiments were conducted on seismic profiling to characterise sandstone rock mass on the basis of P-wave velocity (Vp) measurements. The running benches were selected for the experimentation so as to cross check the results of the Vp with the exposed faces of the benches. The instrument used for seismic profiling contains 24 geophones of 14 Hz frequency. The mode of survey was the „refraction method‟ which could give the Vp profile up to 50-60 m depth and about 100 m stretch. The source of vibration generation was by hammering of specific Sledge hammer. The raw seismic data collected in the field was analysed by a software called ‟Seismic imager‟ for generating a Vp profile of the rock strata. The Vp profiles were determined for three benches of the mine, which include weak, medium and hard type of rock mass. The rock impedance was calculated based on the Vp determined by seismic profiling. This data was used for the selection of explosive with desired velocity of detonation and density, so as to match the impedance of the rock mass. The blast performance with the suitable explosives with impedance matching was obviously better than that of impedance mismatching. Trials were also conducted with heave energy-rich ANFO explosive with mismatched impedance properties and observed better results. The optimisation studies resulted in reduction of back break by 50-75% and reduction of mean fragment size by 15-47%. The paper stresses the need for conducting impedance matching exercise for all the blast sites for blast optimisation and productivity improvement.