Shocked quartzes are specific to large meteorite impacts. They appear at a pressure greater than 200 kb, equivalent to the static pressure of a 2000 kilometre column of water (a 10 metre column of water exerts a static pressure of about 1 bar). Shocked quartzes are only visible under the microscope as thin slivers. They are found for example in the sediments of the famous black layer of the Cretaceous-Tertiary limit. In this case, they are associated with the Chicxulub impact crater and the famous KT event that led to the disappearance of the non-avian dinosaurs.
this grain of shocked quartz shows parallel fracture planes caused by the high pressures of a large meteorite impact. © CRAS/Elsevier/Ph.Paillou