Hertfordshire Geological Society

Church Guides

More churches will be added from time to time.

St Albans Cathedral, both inside and outside

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St Mary’s, North Mymms

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Featured Church: St.Mary’s, North Mymms

The idyllic setting of St. Mary’s church in North Mymms Park

St. Mary’s church in North Mymms Park is just two miles north of Potters Bar and has been a favourite destination of mine for my WEA geology classes.   It exhibits the relationship of church building stones to the local geology to a remarkable degree and also contains a range of monuments inside which show the changing fashion for different types of monumental stone over the last thousand years.  

The main body of the church, the nave, chancel and aisles, is fourteenth century, with St Catherine’s chapel at the end of the north aisle being the oldest part of the building.  The west tower was built nearly a century later and was probably completed about 1450.  The main building material is  roughly knapped flints, which were source locally, with the quoins, doorways and window frames being originally all of clunch, probably Totternhoe stone from Bedfordshire.  The Victorian-age porch has more cleanly knapped flints.

 

Knapped flint on the exterior of the south porch.
The base of the west tower (south side) showing clunch blocks, with HPS block (left) and two pieces of false puddingstone (centre and right) at ground level.

The tower is the most interesting part of the church as far as building stones are concerned.  There are numerous blocks of clunch in different stages of decay, some being replaced by tougher oolitic limestone blocks in Victorian times.  The entire west doorway was replaced by Cotswold oolite in 1992.  Blocks of clunch either side of the doorway are covered in graffiti, including a medieval mass dial and a Victorian ordnance survey bench mark.  At several distinct levels up the tower are impersistent bands of false puddingstone, also known as gravel-stone or ferricrete.  These probably represent the end of an annual building season during the construction of the tower.

West doorway renewed in Cotswold limestone in 1992.
Graffiti on a block of clunch next to the west door.

Towards the base of the south wall of the tower a prominent example of grey Hertfordshire Puddingstone can be compared with several nearby blocks of false puddingstone.  There are also some other pieces of HPS to be seen in the tower and the wall of the south isle.  The tower also contains distinctive pieces of brown to orange vuggy ironstone.  Originally thought to be of Lower Greensand  age,  this rock is a recent iron-pan which can be found in local fields. The HPS, false puddingstone and ironstone are all local ‘field-stones which probably all originated within the parish.

Detail of the Hertfordshire Puddingstone block
Detail of one of the False Puddingstone / Gravel-stone slabs.
Piece of vuggy ironstone 2m. above the HPS block.

Most of the memorials inside the church are of white Carrara marble from Italy.  The most prominent is the massive wall-tomb in the chancel to Lord John Somer in which the three main varieties of Carrara marboe can be seen.  Designed by Peter Scheemaker in 1719, the statue of Justice is of the typical white marble favoured by sculptors and known in the trade as ‘First Statuary’.  Most of the lower panels and the door into the vestry are of a streaked white and grey variety confusingly called Sicilian and the grey marble panel behind ‘Justice’ is probably the variety called ‘Bardiglio’ .   The sarcophagus on which Justice is sitting is of a more exotic yellow streaked black marble, called Porta d’Oro, it is from Liguria on the Italian Riviera.     

 

The Somer memorial in the chancel of St. Mary’s
Carrara marble of the vestry doorway of the Somer’s memorial.
Porta d’Oro marble of the sarcophagus of the Somer’s memorial.

In the north-west corner of the north aisle is an unusual alabaster table tomb of the late sixteenth century, the upper slab of which bears the incised image of Elizabeth (or Mary) Beresford (d.1584).  The image is picked out in black bitumen to stand out against the white alabaster.  The side panels should be examined as they display the typical red streaking and mottling of Derbyshire alabaster.  The oldest memorial in the church is the broken off upper part of a Purbeck marble thirteenth century floriated-cross tomb slab. It is on the floor at the entrance of St. Catherine’s chapel and was only discovered during restoration work undertaken in 1971.

Elizabeth Beresford’s image, on her table tomb of Derbyshire alabaster.
The top part of the floriated-cross tomb slab of Purbeck marble.