Cosmic Impact, Mullite (image) Dartmouth College Caption The high temperatures of the meteorite impact 12,900 years ago produced mm-sized spherules of melted glass with the mullite and corundum crystal structure shown here. Credit Mukul Sharma Usage Restrictions The photographer must be credited. 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.