Monday, May 04, 2009

Hertfordshire Puddinstone - My Town Monday!

This week I am going to tell a little about a very special rock that is only found in the county where I live, its called Hertfordshire Puddinstone. When I was growing up I didn't realise just what it was, to be honest it looks like some sort of concrete holding together a load of pebbles. Dad used to have a lump of it in the front garden of our old house, I am sure it was left there when they moved. (which is a shame!)
So what is Puddinstone??

The picture above is one variation found in the area and it DOES look like concrete with pebbles mixed in!!

So a potted history.....
The flints and pebbles were eroded from the surrounding chalk beds some 56 million years ago in the Eocene period 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 drew out silica from surrounding rocks into the water immersing the flint pebbles. Further drying precipitated the silica which hardened around the pebbles, trapping them in the matrix. Puddinstone is commonly found in river beds, and is less frequently to be seen exposed to the surface.

Oxides of iron were also trapped in the silica, giving rise to many different hues when the puddinstone is examined closely. From a greater distance, puddinstone is generally brown or ginger in colour, although pink is possible. The silica is very hard, which led to use being made of puddinstone as a building material supplementing flintstone buildings such as at St Mary's Church, Stocking Pelham; as a decorative feature or waymark, or, during Roman times, for grinding corn.

The pebbles and surrounding silica have melded into one stone, it is so hard that it regularly breaks farm equipment when it is bought to the surface!

Hertfordshire puddinstone was credited in local folklore with several supernatural powers, including being a protective charm against witchcraft. 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.

Other places in the world have their own types of puddinstone, but the make up of 'our' stone is exclusive to Hertfordshire!! I think I am going to have to go and see if I can find a lump for my garden!!


Mary said...

That is fascinating Lyzzydee. I love traveling from spot to spot and noticing the different rocks and lay of the land.

Manna said...

Fascinating is right! Another great read :)

debra said...

That is really interesting. It does look like concrete with pebbles in it.