Suevite is a shock-metamorphosed rock. It is an impact breccia composed of impact melt and lithic fragments. Impact metamorphism is caused by a collision between Earth and large extraterrestrial body which is usually meteorite or asteroid
According to the IUGS Subcommission, suevite or SueviteBreccia is a polymict impact breccia with clastic matrix and mineral clasts in various stages of shock metamorphism including cogenetic impact melt particles which are in a glassy or crystallized state.
Originally, suevite was the name of a melt breccia in the Ries crater and derived from the province of Swabia in southern Germany, and such means “Swabian stone”. For decades, the Ries crater suevite was considered a peculiar volcanic breccia and unique in the world. Both the volcanic origin and the uniqueness had to be abandoned when the Ries suevite was shown to be a strongly shocked impactite and comparable rocks were found in many other impact structures worldwide.
Significant debate has ensued as a consequence of two publications promoting the idea that suevite from the Ries crater, for 50 years considered a melt-fragment-bearing impactite with an essentially clastic matrix (“particulate matrix” according to, should rather be considered impact melt rock with a melt groundmass. This idea questions the validity of the term “suevite” (and by implication) the entire polymict-impact-breccia nomenclature of the IUGS subcommission.