A dry polishing technique for the petrographic examination of mudrocks

A method of high-quality dry polishing is presented here, in which lubricating agents such as water, isopropyl alcohol, oils and water-based diamond suspensions are eliminated. This method has been developed to avoid various problems that arise through wet-polishing techniques, and to meet the quality requirements for high-resolution microscopy and SEM analysis. The technique has been tested on two epoxy embedded blocks using abrasive silicon carbide papers ranging from 240 (avg. grain size 58.5 μm, Struers) to 2500 grit (avg. grain size 8 μm, Struers), but with different final polishing stages. Both methods show comparable high-quality results, with no optical relief or thermal alteration of embedded organic matter. Such methods could be applied to other rock-types that might be sensitive to the use of any kind of lubricant. The dry-polishing technique enables the high-resolution study of clay minerals and fine-grained sediments using optical and scanning electron microscopy (SEM).