Leaching of Radium within Shale Pores (image) Dartmouth College Share Print E-Mail Caption Radium from within rock leaches from clay minerals that transfer highly radioactive radium-228 and an organic phase that serves as the source of radium-226. Credit Joshua D. Landis. Usage Restrictions Credit to: Joshua D. Landis Share Print E-Mail 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.