Shocked quartz

[1] The presence of shocked quartz supports that such craters were formed by impact, because a volcanic eruption would not generate the required pressure.

[2] Lightning is now known to contribute to the surface record of shocked quartz grains, complicating identification of hypervelocity impact features.

Coesite and stishovite are usually viewed as indicative of impact events or eclogite facies metamorphism (or nuclear explosion), but are also found in sediments prone to lightning strikes and in fulgurites.

[5] Lightning also generates planar deformation features in quartz and is capable of propagating appropriate pressure/temperature gradients in rocks and sediments alike.

[7] Though shocked quartz is only recently recognized, Eugene Shoemaker discovered it prior to its crystallographic description in building stones in the Bavarian town of Nördlingen, derived from shock-metamorphic rocks, such as breccia and pseudotachylite, of Ries crater.