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Hertfordshire Puddingstone is a conglomerate of very well rounded flint pebbles, embedded in a matrix of fine pale coloured sand, all bound together by hard natural silica cement. Most of the pebbles are coloured ochre or red, or a mixture, and have black rims.  We are sure the colours are limonite and haematite, with the black rims possibly being goethite but exactly how the iron staining occurred is not known at present.  A group of East Herts Geology Club members is actively researching local Hertfordshire puddingstone in our area to try to answer this, and other questions.  For a paper by EHGC members Bryan Lovell and Jane Tubb click here - and here for a recent update

For a leaflet  click here

There are other puddingstones but only Hertfordshire Puddingstone has all the features illustrated below

The matrix is
fine pale sand

Most pebbles have black rims
and are coloured ochre and/or red

Pebbles are very well rounded.

Pudstone 4


It is cohesive, so breaks cleanly
across pebbles and matrix

Cementing was patchy, so pebbles
on the edge of blocks stand out