Mt. McRae Shale With Pyrite Nodules (image) University of Maryland Share Print E-Mail Caption A geological rock hammer used as scale against a sample of the organic-rich 2.5 billion year old Mt. McRae Shale with pyrite nodules. Credit Photo by A. Jay Kaufman Usage Restrictions Must give credit as: Photo by A. Jay Kaufman 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.