Sediment Slurry (IMAGE) Duke University Caption These are coal ash samples going through a chemical extraction process to test the amount of rare earth elements present in them. Credit Heileen Hsu-Kim, Duke University 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.