Here we meet the flintstones of Ardleigh.
Please send answers to me (not Fred and Wilma) to the following questions via email or the message centre:
1) Compare the flints cladding Southwark Cathedral from the photo in the gallery with the flints here in Ardleigh. Please describe the differences between them including colour and shape. Referring to the common features of natural flints below, which could be described as more "natural"?
2) In the buttress to the right of the south door, look at the stone between the two "stars" (highlighted on the sketch in the gallery). Please describe the differences between this stone and the ones surrounding it. From the three types of chalcedony below, what type do you think we have here and why? As it's embedded in a wall, and shining light through is impossible, please offer your best guess.
3) Please take a photo of yourself, part of yourself or something belonging to you in front of this beautiful church, without giving away the answers and attach to your log.
Chalcedony
Chalcedony is formed of microcrystalline quartz or in other words tiny crystals of silicon dioxide (SiO2) and is formed in chalky limestone rocks. The silicon dioxide is derived from the bodies of sponges and other ancient sea creatures. This silicon dioxide has dissolved and then trickled through fissures and burrows in the sea floor and is then hardened and compressed over millennia to form odd-shaped nodules, usually coated in a pale chalky layer derived from the original surrounding stone.
Flint AKA Chalcedony
Flint is a type of chalcedony. When cross sectioned, the chalky layer surrounds the waxy but lustrous flint, which is usually dark in colour but can vary considerably and can have inclusions, but never banding. Flint is either slightly translucent or opaque.
Agate AKA Chalcedony
Agate is also a type of chalcedony. It is chemically exactly the same as flint and formed in a similar way except it is formed gradually in layers. Impurities in the silicon solution can cause banding to occur. Agate is always translucent - it will let some light through and this is the key method for identifying agates. Agates can be formed in volcanic areas, but have also been found in chalky limestone.
Jasper AKA Chalcedony
Jasper is also a type of chalcedony and chemically similar to both agate and flint. It is formed when fine particulate (non silica) minerals are cemented together by silicon dioxide. Jasper is always opaque because the non-silica content is too high to allow light to permeate. The colour of jasper is derived from impurities in the particulate minerals and jasper is often strongly coloured.
These rocks are not mutually exclusive and it is possible to find jasper and agate in the same rock where some parts are translucent, and some are not.
Reference:ย https://rocktumbler.com/blog/what-is-agate-jasper-chalcedony/ (Accessed Jan 2026)