The application of engineering geophysics to the characterization of rock masses is exemplified through a case study of three phases of a research project into the design of efficient blasting systems in open-pit mining. Seismic experiments are used before and after mine blasting to monitor the efficiency of explosions in terms of rock fragmentation. Spectral analysis of seismic signals, after they have been used to interrogate rock masses, is used to compute preblast and postblast attenuation and velocity parameters. The results show that fragmentation efficiency of a mine blast and fracture anisotropy of a rock mass can be quantified in terms of three-dimensional (3-D) attenuation spectra and polar anisotropy diagrams. These seismic data are correlated with the blast design and the energy used by the excavating dragline machine to dig to rock mass. An overview of the seismic attenuation technique and instrumentation used in the project (phases I and II) is given. A case study from phase III highlights the scope and interpretation of the relationship between excavation parameters and seismically characterized blasting efficiency.