Hertfordshire puddingstone

Hertfordshire puddingstone is a conglomerate sedimentary rock composed of rounded flint pebbles cemented together by a younger matrix of silica quartz.

The distinctive rock is largely confined to the English counties of Buckinghamshire[1] and Hertfordshire but small amounts occur throughout the London Basin.

The flints were eroded from the surrounding chalk beds some 56 million years ago in the Eocene epoch and were transported by water action to beaches, where they were rounded by wave erosion and graded by size.

A lowering of sea levels and general drying during a brief arid period known as the Paleocene–Eocene Thermal Maximum drew out silica from surrounding rocks into the water immersing the flint pebbles.

A fragment of a quern-stone made from puddingstone was found by archaeologist Dominic Shelley on the site of a Romano-British farmstead in Great Eversden, Cambridgeshire.

Parish records from the village of Aldenham relate that in 1662 a woman suspected of having been a witch was buried with a piece of it laid on top of her coffin to prevent her from escaping after burial.