This shocked quartz grain is from the upper part of the crater-fill deposits at a depth of 820.6 ft in the core. The corehole is located at the NASA Langley Research Center, Hampton, VA, near the southwestern margin of the Chesapeake Bay impact crater. Very high pressures produced by strong shock waves cause dislocations in the crystal structure of quartz grains along preferred orientations. These dislocations appear as sets of parallel lamellae in the quartz when viewed with a petrographic microscope.
Bolide impacts are the only natural process known to produce shock lamellae in quartz grains.
USGS field investigations of the Chesapeake Bay impact crater during year 2000 are conducted in cooperation with the NASA Langley Research Center, the Hampton Roads Planning District Commission, the Virginia Department of Environmental Quality, the Virginia Division of Mineral Resources, and the Geology Department, College of William and Mary.