St Chad's Church is believed to be the oldest building in Stafford Town Centre, with a history reaching back into the twelfth century, and possibly beyond. The main part of the church is richly decorated; patterns and figures have been carved into almost every archway and pillar. Father Michael Fisher explained that the Norman kingdoms were as far reaching as the Mediterranean and the Middle East, and this is why the stonework has a Celtic, Nordic, and Byzantine look.
It's believed that the carvings were made by a group of stonemasons from the Middle East who came to England during the Crusades.The church is mainly built from grey sandstone quarried in Tixall, just a few miles from Stafford.The carvings would have been made on site, and Father Fisher thinks the masons would have been allowed some creative freedom.One of the main archways is completely covered in carvings of owls with crossed wings, and there are lots of carvings of serpents around the pillars too.The serpents are said to represent, or pay homage to, the founder of the church, who was called Orm.According to the County Records, Orm was the name of a man who lived near to the East gate of the church.There is an inscription on a pillar which reads" Orm Vocatur Que Me Condidit", which is translated as "the man who established me is called Orm".
Sandstone Basics
Sandstone is a type of rock made from sediment — a sedimentary rock. The sediment particles are clasts, or pieces, of minerals and fragments of rock, thus sandstone is a clastic sedimentary rock. It is composed mostly of sand particles, which are of a medium size; therefore, sandstone is a medium- grained clastic sedimentary rock. More precisely, sand is between 1/16 millimetre and 2 mm in size (silt is finer, gravel is coarser). The sand grains that make up sandstone are aptly referred to as framework grains.
Mature continental sediment consists of a handful of surface minerals, and sandstone, therefore, is usually almost all quartz. Other minerals—clays, hematite, ilmenite, feldspar, amphibole, and mica— and small rock fragments (lithics) as well as organic carbon (bitumen) add color and character to the clastic fraction or the matrix. A sandstone with at least 25 percent feldspar is called arkose. A sandstone made of volcanic particles is called tuff.
The cement in sandstone is usually one of three materials: silica (chemically the same as quartz), calcium carbonate or iron oxide. These may infiltrate the matrix and bind it together, or they may fill the spaces where there is no matrix.
Depending on the mix of matrix and cement, sandstone may have a wide range of colour from nearly white to nearly black, with grey, brown, red, pink and buff in between.
How Sandstone Forms
Sandstone forms where sand is laid down and buried. Usually, this happens offshore from river deltas, but desert dunes and beaches can leave sandstone beds in the geologic record too. The famous red rocks of the Grand Canyon, for instance, formed in a desert setting. Fossils can be found in sandstone, although the energetic environments where sand beds form don't always favor preservation.
When sand is deeply buried, the pressure of burial and slightly higher temperatures allow minerals to dissolve or deform and become mobile. The grains become more tightly knit together, and the sediments are squeezed into a smaller volume. This is the time when cementing material moves into the sediment, carried there by fluids charged with dissolved minerals. Oxidizing conditions lead to red colors from iron oxides while reducing conditions lead to darker and greyer colours.
Geology of cross bedding:
In geology, the sedimentary structures known as cross-bedding are the (near-) horizontal units that are internally composed of inclined layers. This is a case in geology in which the origional depositional layering is tilted, and the tilting is not a result of post-depositional deformation. Cross-beds or "sets" are the groups of inclined layers, and the inclined layers are known as cross strata.
Cross bedding forms during deposition on the inclined surfaces of bedforms such as ripples and dunes, and indicates that the depositional environment contained a flowing medium (typically water or wind). Examples of these bedforms are ripples, dunes, anti-dunes, sand waves, hummocks, bars, and delta slopes. Cross-bedding is widespread in many environments. Environments in which water movement is fast enough and deep enough to develop large-scale bed forms fall into three natural groupings: rivers, tide-dominated coastal and marine settings.
COLOURS OF SANDSTONE
The colour of a sandstone depends on its detrital grains and bonding material.
- An abundance of potassium feldspar often gives a pink colour.
- Fine-grained, dark-coloured rock fragments, such as pieces of slate, chert, or andesite, however, give a salt-and-pepper appearance to a sandstone.
- Iron oxide cement imparts tones of yellow, orange, brown, or red.
- Calcite cement imparts a grey colour.
- A sandstone consisting almost wholly of quartz grains cemented by quartz may be glassy and white.
- A chloritic clay matrix results in a greenish black colour.
Please note DO NOT DRIVE to this church! It is in the pedestrianised centre of Stafford. There are plenty of pay and display car parking nearby, alternatively Asda car park is a few minutes walk and you can park here for free for a limited duration.
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To log this earthcache please message or email the answers via our profile. DO NOT put the answers in your online log. Any spoiler pictures will be deleted. Look around the doorway arch and the larger blocks to the RIGHT of the main door (below waist height) then to the LEFT of the door higher up and answer the following questions:
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1. Sandstone can come in different colours. Describe the colours can you see in the stone?? What impurities are present in some of the stone blocks (in the above listing for the information on sandstone colours and impurities)
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2. Other than local availability, why was sandstone often chosen for decorative buildings? Can you give some specific examples of what you can see on the building to back up your answer?
- 3.Sedimentary rocks are often deposited in layers and there is clear layering in some of the blocks. Some of the blocks contain cross bedded layers ( refer to text on cross bedding ). A=Approximately what angle in degrees do the layers appear in the stone? B=What thickness are the bands, are they all the same and uniform or are some thicker than others??
- 4. Alterations to the building and repairs mean you will see differences in the stone and new stone blocks in some places. Please take a look at the new stone work, IN YOUR OPINION, Is this Tixall Grey Sandstone? You will need to look closely and please explain your reasoning for your answer.
- 5. Finally, to prove you have visited the site and are not armchair logging, there is a metal hook in the wall behind the war memorial, knee high. What shape is the baseplate that the hook is attached to?
- 6.Please supply a photograph of yourself and/or your GPS at the front of the Church as further proof of your visit, As per Earth Cache logging requirements, faces are not necessary.
Pictures are welcome as long as they are not showing any of the answers!
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