The article discusses how blasting activities in all four pits at Thunder Basin's Black Thunder mine (USA) are focused on cast efficiences. With widths varying from 190 ft to 265 ft and bench heights varying from 90 to 175 ft, casting efficiencies vary with differing geometry. For example, the percent cast to final in the 200-ft pit is on the average higher than the 270-ft pit. The powder factors are somewhat higher in the narrower pits, thus increasing the cost of blasting. This leads to a very detailed look at the acutal benefit of cast blasting and the associated costs.