Largest cannonball concretions
- Who
- Frontier Formation, Rock City, Kansas
- What
- 6 metre(s)
- Where
- United States
- When
- known about since prehistory; Late Cretaceous period
Cannonball concretions are roughly spherical boulders formed by the natural cementation of sand by the mineral calcite. The largest examples are up to 6 m across and are found in Rock City, Kansas, USA, as well as in central Wyoming and northeast Utah, USA, where they are associated with the Frontier Formation of the Late Cretaceous period.
The concretions at Rock City consist of around 200 individual boulders in three separate clusters.