Geology Site Account

Site name: 'Millennium stone', Navestock

Grid reference: TQ 5461 9615

Brief description of site:

A very large boulder of ferricrete that was placed on a concrete plinth in 2000 to celebrate the Millennium. It has a plaque describing the boulder, incorrectly, as a 'puddingstone'.

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Summary of geological interest

At the hamlet called Horseman Side a giant boulder of ferricrete (210cm x 150cm x 60cm) sits on a concrete plinth by the road. It is was placed here in 2000 to mark the new millennium. The boulder was excavated from a neighbouring field.

Although the engraving on the plinth states that it is a puddingstone, it is, in fact a ferricrete, which is an iron-cemented gravel.

Good building stone is rare in Essex and East Anglia but one exception is the rock ferricrete. In Ice Age gravels the movement of iron-rich groundwater has resulted in the formation of hard, solid masses of ferricrete which is an iron pan at the level of the water table. It is basically an iron-cemented gravel but it can be extremely hard and durable. Ferricrete has been used in the construction of several Essex churches.

The Millennium Stone, Navestock. Photo © G. Lucy