St. John's Church in West Wickham

 

The Church of St. John the Baptist in West Wickham

The day after a very productive investigation of the ‘urban geology’ of Crystal Palace Park, including the 'dinosaurs' and the 'Geological Illustrations', I set off from Corkscrew Hill in West Wickham to explore the Keston Common gravel pit, a recommended RIGS (Regionally Important Geological Site) where the Blackheath Member of the Eocene Harwich Formation is exposed. 

 

The geology of the area around West Wickham and Keston

As for my walks in South Yorkshire, I had prepared a list of buildings to photograph for the British Listed Buildings website - including the Grade II* Listed Church of St. John the Baptist, which dates to c.1490 and incorporates earlier stonework but was substantially rebuilt in 1844-47 by John Whichcord, with later additions. 

 

The approach to St. John's church

 

Passing through the lychgate, I firstly stopped to look at the organ chamber (1889), which is built in a chequered pattern, with knapped flint nodules and ashlar panels and quoins of a grey shelly limestone that I am not familiar with. 

 

A detail of the masonry to the organ chamber

The thinly bedded rock-faced walling forming the lower part of the organ chamber is also very shelly, with the same colour, but it contains several blocks that are very fine grained and muddy looking and contains no shell fragments. 

 

A detail of the rock-faced walling to the organ chamber

Moving on to the tower, which is offset to the south-west of the nave, this was rebuilt in flint along with the nave and the north aisle as part of Whichcord’s restorations, with Bath stone used for the restored late C15 straight sided arched windows. 

 

The tower

 

The south doorway in the tower also has a surround that is made in Bath stone, which at low level can be seen to be typically cream/beige in colour and contains distinct shelly beds, which are highlighted by differential weathering of the calcite cement. 

 

A detail of the Bath stone to the south door

 

The quoins and cappings to the buttresses, however, are made of an iron rich sandstone with a well developed greyish patina. This is another building stone that I was not familiar with, although West Wickham is not that far from sources of the Cretaceous Wealden sandstones. 

 

Sandstone quoins to a buttress

When having a look at the north side of the church, I found a lump of a fine grained yellow sandstone, which appears to be from a failed moulded section from one of the buttresses. It contains rusty brown and occasional black streaks along the bedding planes and does not react with hydrochloric acid, which would probably rule it out as being Reigate stone. 

 

A sample of fallen sandstone from the north elevation

In 1961, an extension was added to the north elevation and another floor was added to the Lady Chapel, which are again built with knapped flint, with a streaky yellowish sandstone also being used for the dressings. 

 

A view of the north elevation

 

On the north wall of the Lady Chapel, the lower few courses of masonry comprises alternating courses of knapped flint and irregular and roughly squared blocks of an off-white stone, which has a noticeably very pale green tinge and is also used as scattered blocks in the stonework above. 

 

A detail of masonry to the Lady Chapel

Without touching it, I could see that it was much more friable than the sandstone used for the dressings, with the surface generally decaying and laminating, and I found a few pieces lying on the ground that had become detached from the masonry. 

 

A detail of the sandstone masonry to the Lady Chapel

The samples that I collected are extremely fine grained and feel slightly gritty when rubbed with my fingers, but using a hand lens I can’t distinguish any individual grains; however, very fine specks of dark green glauconite are disseminated throughout the stone, which catch the light and the stone reacts strongly with hydrochloric acid. 

 

Samples of calcareous and glauconitic sandstone

Although the Reigate Stone that I have seen is darker and greener, Historic England’s Building Stones of England Atlas for Kent describes it as pale grey to off-white calcareous siltstone and, sometimes, resembling chalk from a distance. From one of the samples, I crushed a small piece that had broken off and covered it with hydrochloric acid until it stopped effervescing, which left a residue of green/grey silt like material. 

 

A glauconitic silty residue

 

After finding a couple of samples of very white oolitic limestone, which I presume have been left behind after restoration of the windows, I was invited by the churchwarden – who I had first met when arriving at the church more than an hour earlier - to take another look at the interior and enjoy a cup of tea before the Annual General Meeting. 

 

White oolitic limestone

 

Even though, as a geologist, I have developed specialist stone identification skills since working in the building restoration industry in London, I have to say that the very fine grained white stone used for the arcade and arches took me quite by surprise and it has made me wonder if these are actually examples of Chalk and not Portland limestone, which is the most common building stone in the capital.

 

Views of the arcade and arches