Suevite Identification Guide

What Suevite Looks Like

Suevite is an impact breccia, a rock formed by meteorite impact, consisting of angular fragments of country rock and mineral grains set in a fine-grained matrix that contains melt particles and glass. It is typically gray to greenish-gray or brownish, poorly sorted, and chaotic, with clasts of many different rocks jumbled together. Its hallmark is the presence of shocked minerals and impact melt glass (including aerodynamically shaped glass bombs and contorted glass shards called Flädle), not present in ordinary volcanic or sedimentary breccias.

Step-by-Step Field ID

1. Check for chaotic breccia texture. Angular, poorly sorted clasts of varied rock types in a fine matrix.
2. Look for impact melt glass. Dark, contorted glassy fragments (Flädle) and devitrified glass within the matrix.
3. Hunt for shock features. Under magnification or in thin section, look for planar deformation features (PDFs) in quartz, shatter-coned clasts, and high-pressure minerals (coesite, stishovite) or diaplectic glass.
4. Note mixed clast sources. Fragments from several different bedrock units jumbled together suggest an impact, not a single volcanic vent.
5. Consider geologic context. Found in or around a known/suspected impact crater.

Key Diagnostic Tests

• Hardness/streak: variable, since suevite is a rock of mixed minerals; not diagnostic on its own.
• Shock metamorphism: PDFs in quartz, shatter cones, and high-pressure silica polymorphs (coesite, stishovite) are the definitive impact signatures (microscope/lab).
• Glass content: presence of impact melt glass and diaplectic (shock-amorphized) glass.
• Texture: unsorted polymict breccia with melt particles.

Common Look-Alikes

• Volcanic breccia / ignimbrite (tuff): also contain glass and fragments but show volcanic textures (welded shards, pumice, consistent volcanic clast suite) and lack shock features like PDFs and coesite.
• Tectonic/fault breccia: angular clasts from cataclasis but no melt glass and no shock minerals.
• Sedimentary breccia/conglomerate: clasts cemented by ordinary minerals, no glass or shock features (and conglomerate clasts are rounded).
• Pseudotachylite: dark melt-bearing rock from faulting or impact; distinguished by context and by the presence (or absence) of shock minerals.

Where It Is Found

Suevite is found at and around meteorite impact structures. The type locality is the Nördlinger Ries crater in Germany (where it was used as building stone); other occurrences include the Chesapeake Bay, Chicxulub, Popigai, and other confirmed impact craters worldwide.