Rock Fulgurite (IMAGE) University of Pennsylvania Caption The study examined a rock fulgurite -- a thin layer of glass that forms when lightning strikes a rock's surface. The sample was collected from northern Italy's Mount Mottarone. Credit Reto Gieré Usage Restrictions In context of reporting 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.