Golden Crystals (IMAGE) Proceedings of the National Academy of Sciences Caption Golden crystals of iron sulfide -- pyrite -- contain information about Earth's atmosphere around 2.5 billion years ago. Credit Image credit: Matthew Robert Warke 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.