**This cache is located within an area frequently patrolled by Police. Please avoid acting suspiciously whilst searching for it, and if challenged, explain about geocaching**
 

Meet the Flintstones

Church House

You are standing in front of Church House, the home of the Church of England. This is the second such building on this site, with the current building opened in 1940 by King George VI. The building was designed by Sir Herbert Baker, whose tomb is nearby in Westminster Abbey. Prior to his work on Church House, he had designed many buildings in South Africa and India during the colonial period.

As work was completed during the Second World War, and given the building's location in Westminster, it was at risk from German bombing. In fact, the building survived such an attack, and because of fears of the Houses of Parliament being bombed, both the House of Lords relocated for a time to Church House. Following the war, after the United Nations was formed at nearby Methodist Central Hall, the first meeting of the UN Security Council took place at Church House.

Flint

Of course, this is an EarthCache, we're not here to tell you only about the history of the building but the geology of the construction materials used as well. In particular, the use of flint across the lower level of the building. This was specifically chosen by Baker, as flint is often used in older churches and so he wanted to reflect that in his design.

Flint actually forms as nodules of quartz within other sedimentary rocks, such as limestones. It is considered to be a cryptocrystalline, which means that the crystalline nature of the rock can only be revealed microscopically. It is formed as a result of a chemical reaction within the parent stone; for example, it forms in chalk as a result of bacterial activity in the seabed creating hydrogen sulphide which then combined with dissolved oxygen creating an acidic reaction that dissolves the alkaline chalk and precipitates silica (originating from the skeletal structure of marine animals) to create flint. This process in which a crystalline solid is formed from a liquid or vapour is known as nucleation.

Flint comes in a variety of colours, which is caused by impurities in the rock, for example from minerals such as iron. Flint is comprised of quartz, and it is harder than the surrounding limestone in which it is found. This coupled with the irregular shape of the nodules, means that it can sometimes be mistaken for fossils. However, unlike igneous and metamorphic rocks, as flint is a sedimentary rock, it is possible to find fossils within these stones. Due to the process required to create flint, these will be aquatic creatures, such as sponges, sea urchins (echinoids), small shellfish or trace fossils (this is where traces of an animal are fossilised, i.e. a burrow).

Questions:

In order to log this EarthCache, please go to the coordinates indicated and study the flintstones in the exterior wall of Church House.

1) Describe the texture and features of the stones. Do they appear in regular or irregular sizes? What colours can you see? Are the individual stones a single colour, or can any patterns or general characteristics be seen? What do you think caused this?

2) Look for an unusual looking stone to the right of the doorway. It is the third stone away from the "14", if you count down at around 135 degrees. Describe this stone, what is the texture and features? How does it differ from the other stones around it?

3) Why do you think this stone is different to the others? What could it be instead? How do you think this was formed?

Please send in your answers via the messenger service or by email.