Dyffryn yr Ithfaen - The Granite Valley EarthCache
Hidden : 11/21/2012
Difficulty:
2 out of 5
Terrain:
1.5 out of 5

Size: Size: not chosen (not chosen)

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Geocache Description:

Dyffryn yr Ithfaen - The Granite Valley


This valley lies in the shadow of the three peaks of Yr Eifl on the northern side of the Llŷn Peninsula. The Eifl's central summit is the highest point on the Llŷn Peninsula.

The geological phenomenon

Lining the mountainsides of the valley are large deposits of granite, an extremely hard type of rock formed from cooling magma. The hardwearing qualities of granite made it a popular material during the Industrial Revolution as it was used to build tunnels, bridges, pavements and roads throughout the country.


What is the origin of the Granite ?

The granite is the ubiquitous component of the earth crust. It has crystallized from magma. The Fractional crystallisation have reduced the melt in iron, magnesium, titanium, calcium and sodium, and enrich the melt in potassium and silicon. Alkali feldspar (rich in potassium) and quartz (SiO2), are two of the defining constituents of granite.
The final mineralogy, texture and chemical composition of a granite is often distinctive as to its origin. For instance, a granite which is formed from melted sediments may have more alkali feldspar, whereas a granite derived from melted basalt may be richer in plagioclase feldspar.
Granite has a slow cooling process which forms larger crystals.

The quarry

Because of its location by the sea the Nant seemed to be a perfect location to establish a quarry.
During the nineteenth century, as granite was in great demand, three quarries was established in the valley : Cae'r Nant, Porth y Nant, Carreg y Llam.
A Liverpool company bought the Nant in 1861 and built accommodation barracks for workers who travelled from afar during the working week.
In 1900, around 2,000 quarrymen had found employment along a five mile stretch of coastline, on the north Llŷn Peninsula. In 1911, Nant Gwrtheyrn merged with other local quarries to form part of the Welsh Granite Company.
The Nant's granite quarries were badly affected during the early years of the twentieth century as tarmac became the preferred road surface, which led to the closure of the quarries in the 1940s.

Men who moulded the mountain

At their peak, the three quarries employed around 110 men.
Rock men drilled holes into the rock face to set explosives, which would bring down hundreds of tons of rock.
'Pop-drillers' and 'breakers' used hammers and gun powder to break the granite into more manageable sizes.
Blockers determined how many small sections or cubes were formed from the rock.
Settsmen used a dressing hammer to shape the rocks into perfectly formed brick-like setts.
Labourers, trammers and brakemen brought the granite down to the crushing mill and docks.

The technique of cutting setts

What is a sett ?
A slab of granite dressed into square or rectangular blocks.
Settsmen worked on their feet and used a range of hammers:
- The Sccabler was used to break the crust of the rock.
- The Sledge hammer or Moli mawr was the heaviest of the settman's tools.
- An Iron Gauge or meidrydd was used for the accurate measuring of the setts.
- The hammer without an handle weight ten pounds. It would be sharpened on one end and was used on large rocks.
- The double handed hammer was used to create a hole by hand, one was used to turn the borer and the other would hit the stone.

Earthcache validation

There is no container to seek or logbook to find out.

To validate your visit:
Tell me by mail :
1) How many hammers can you see on the rock close to the coordinates ?
2) What was the weight of the Sledge hammer ? (you can find the information on the panel close to the coordinates)
3) Break a granite stone in half (or find a newish surface exposed) and describe the surface exposed. What is the crystal size ? Could you imagine the reason of that size ?
4) Identify 3 colors of minerals.

Once the mail is sent, you can directly log your visit as "Found it".
In case of problems in your answers, you will be contacted thereafter.

Feel free to add a photo to your log ...
Have a good visit!

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