🇮🇪 Dublin...All that Glitters is not Gold. EarthCache

Dublin is a historic city, one which takes you back in history thousands of years. Though look around and you quickly see much older history in the form of geology. The geology goes back millions of years, indeed 330 millions of years. This EarthCache takes you to look at a geological feature which has featured quite prominently in the buildings of Dublin. 

The EarthCache takes you to the wall alongside the pavement on Saint John's Road West. The below photograph shows where to look. It is wheelchair and pram accessible 

The stone that forms the wall is on the whole limestone.  Limestone is a sedimentary rock, formed bybthe accumulation of lime mud and the shells of ancient sea creatures in a shallow tropical sea. To be more specific, the type of limestone is known as Calp Limestone, which is the bedrock on which Dublin sits. You are truly looking at old Dublin here. We are here however to look at a feature in the indicated limestone rock. You will need to look closely, and it may help to take a photograph and then enlarge it so as to get the best out of this EarthCache.  We are here to look at Iron Pyrite, otherwise known as Fools Gold.  

➡️ So what is Iron Pyrite?

It is an Iron Sulphide, and is found in all types of rock – (igneous, metamorphic and sedimentary) as well as in hydrothermal vents. Its formation can be in a variety of ways:

Igneous Rocks. In this situation it is formed from the minerals in magma, which seperated out, depending on the temperature as it cooled, with crystals being formed. 

Metamorphic Rocks. These rocks are formed by heat and pressure, and in this situations, the pyrite could have been formed as the process of metamorphism takes place, or as a replacement mineral in the rock.

Sedimentary Rocks.  With this type of rock, pyrite is usually found as a replacement mineral,  when  iron and sulphur present in the sediments combine to replace the original chemical composition of organic matter.                               

Pyrite crystals can form as framboids or cubes  depending upon the temperatures and pressures.

Cubes commonly form as a result of fluid rich diagenesis or low-grade metamorphism. Diagenesis means the change of a rock, after initial deposition  into a different form. It can take place due to a chemical, biological and physical change due to reasons such as  temperature, pressures, and saturation with groundwater. They are formed due to authigenesis, which occures when a mineral deposit is produced where it is found. Once the cubes have formed, the pyrite becomes refractory, and can keep its features even when the rock has becomes deformed. Refractory means it is  resistant to decomposition by heat, pressure, or chemical attack.

Framboids have spherical features, like the parts of a raspberry. 

➡️ Dublin and the Pyrite Problem. 

The Calp Limestone was commonly used as building stone, and also for aggregates/ hardcore beneath the flooring slabs in buildings in Dublin and other parts of Ireland.  Rocks which were rich in Iron Pyrite caused a problem, as when exposed to the air and water, the iron pyrite oxidised, meaning it basically changed its structure, leading to expansion of rocks forming the aggregates and hardcore, leading to problems within the buildings such as cracking of walls, and significantstructural damage. . It has become such a big problem, that the Irish government formed the Pyrite Resolution Board, to help home owners with remedification of  the damage caused by the iron pyrite.

This being an EarthCache, in order to log it, I ask that you complete the below tasks. Please send the answers  to me, and do not include them in your log. You can send them to me by using the message facility or email, both of which can be found by looking at my profile. Geocaching is an enjoyable activity, so please do not be put off undertaking the EarthCache. It is not meant to be a test or difficult, just something you can learn about geologically. 

1. Please examine the rock, and explain how the iron pyrite appears, in terms of colour and are there cubes or framboids.  Is the iron pyrite all over the rock, or just in a certain part?

2. If you were here explaining it to someone with no knowledge of geology, how in your own words would you describe the Fools Gold geologically?

3. Please have your photograph taken, or that of your device pointing towards the specific rock. Please date stamp the photograph using your Geocaching name, date and time. Or if you wish write on a piece of paper. Please do not reveal any answers to the questions.