Impactite
Any rock created or changed by a meteorite impact, including shocked rocks, impact breccias, impact melt rocks and impact glasses.
Impactite is the collective name for rocks that owe their character to an impact. The term covers several families. Shocked rocks keep their original structure but carry shock damage such as planar deformation features in quartz. Impact breccias are made of broken fragments, some containing melt particles, such as suevite. Impact melt rocks crystallised from rock melted by the impact. Impact glasses cooled too quickly to crystallise. Many classifications also include tektites, which are glasses flung far from their crater.
Impactites hold the evidence needed to confirm an impact and to date it. They may also contain traces of the projectile itself, recognised from elevated nickel, iridium or chromium, or from distinctive isotope ratios.
A spectacular example is Libyan Desert Glass, pale yellow glass found scattered over the sand in western Egypt, near the Libyan border. It formed about 29 million years ago and is widely considered an impact glass, although no source crater has been confirmed. Suevite from the Ries crater in Germany is another classic. Impactites are recognised by shocked minerals, glass with unusual textures, and their position in or around an impact structure. Protected sites need permission before any sampling.
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