Puddingstone with large pebbles
Puddingstone outcrop on Coppet Hill Puddingstone is common in this area of the Wye
valley from here towards Monmouth
. Some forms were 'mined' and shaped into millstones
for their abrasive qualities.
Puddingstone is a kind of sedimentary rock. It is formed when pebbles, perhaps from a shingle beach, are cemented together by silica coming out of solution.
The rock which forms is extremely hard and resistant to wear. It is used for grindstones and building. The pebbles are usually made of flint, and both they and the matrix are made of silica.