Origin of Friction (IMAGE) National Institute for Materials Science, Japan Caption We removed moisture from the space between the muscovite surfaces by applying high pressure under dry conditions. We then measured frictional forces between the muscovite surfaces at different sliding positions. The results of this experiment closely coincided with frictional forces estimated using quantum mechanical calculations, indicating that the frictions occurring between clay minerals are controlled by atomic-scale electrostatic forces. Credit NIMS Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.