Suevite
A polymict impact breccia containing fragments of glass or melt, alongside shocked rock and mineral clasts, in a fine-grained matrix.
Suevite is an impact breccia with a mixture of clasts from many target rocks (polymict) and, crucially, inclusions of impact melt, usually glass. Its name derives from Suevia, the Latin name for Swabia in southern Germany, and its type locality is the Ries crater, about 24 kilometres across and nearly 15 million years old. In the Ries, the melt particles are often flattened, aerodynamically shaped bodies locally called Fladen, set among crystalline and sedimentary clasts that show all stages of shock metamorphism, from planar deformation features to complete melting.
Suevite occurs both outside the crater rim, overlying the Bunte Breccia ejecta, and as a thicker fallback deposit filling the crater. How it was emplaced, whether by collapse of an ejecta plume, by ground-hugging flows of melt and debris, or a combination, remains debated. The term is now applied to similar rocks at many structures.
The Ries suevite has historic importance: in 1961 the identification of coesite in it helped establish the Ries as an impact structure. It was long used as a building stone, and St George's Church in Nördlingen is built largely from it. In hand specimen, look for grey, porous breccia with dark glassy inclusions.
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