This paper is concerned with processing, analyzing and interpreting drill data. Our ultimate goal is to optimize mining operation by using information extracted from drill logs. Several factors that have great effects on the rotary drilling process are analyzed. To optimize drilling operation, relationships between the rate of penetration and the speci®c energy with other parameters were examined and analyzed by using real operation data, which yielded a set of optimal operating parameters. The concept of rock drillability is discussed. Two new parameters are introduced as drillability indicators. A series of maps constructed are useful as easy-to-understand visual frameworks for collecting, organizing, displaying and evaluating data. Results of this work have the potential to increase productivity and to reduce production cost by improved blast design and optimized drilling processes.