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A line in the stone EarthCache

Hidden : 11/19/2018
Difficulty:
2 out of 5
Terrain:
3 out of 5

Size: Size:   other (other)

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Geocache Description:


To claim a find on this EarthCache you will need to visit the location given, gather some information by reading the listing below and looking around.

Then you need to ether email or message the answers to me.

Please feel free to send your answers and claim your find at the same time.

Please take only photographs and leave only foot prints.

This is placed on a clear footpath which leads to Cae Amos Bothy. I have included a trail head marker and parking.  The climb up is gentle and easy to follow but can be very wet.

 

52.979292, -4.227374 Trail head where the path leaves the tarmac road

52.978822, -4.233847 Parking on a grass verge for a single car

52.977657, -4.235873 Off road parking for several cars

 

Sandstone is a type of sedimentary stone created by rivers and in Aeolian deserts, which wash down small particles of rock, usually in fast flowing erosive rivers, or blown by winds.  As the particles carried in the water moves to slower flowing areas the particles sink to the river or delta bed and build up.  Over millennia these deposits build up, are compressed by the weight above and form hard durable stone.  

The sandstones here were deposited from vast braided river systems, including estuaries and deltas during the Carboniferous (Namurian- Westphalian) 320-310 million years ago and consist of different types of mineral grains.

 

On occasion, as the rock is forming minerals can seep into cracking either vertical or horizontal and form small seams of more concentrated crystals within the rock, it precipitates out in small cracks in many rocks causing what appear to be  veins.  The veins are much harder than the rock around them which means that when the rock is eroded they can be left behind.  This leaves a line in the rock, often at odds to the bedding plane (direction of sedimentation)

 

The lines you see are occasionally cross-cutting, which is a common feature of mineral veins in rocks. They protrude out of the rock, which tells you that it's very resistant material, relative to the host rock. This is an extremely common phenomenon.

Types of common minerals that can be deposited in Sandstone.

Quartz is a mineral made mostly of silicone and oxygen atoms in a continuous framework of SiO4 silicon–oxygen pyramids, with each oxygen being shared between two tetrahedral silicone atoms. Quartz is the second most abundant mineral on Earth' crust.  Quartz is primarily see through in its purest form but small imperfections in its formation will mean that it usually has some colour.  Quartz can be clear, white, pink, red and other colours depending on what impurities are contained within.  At this location, if you are looking at a quartz vein it will be white.

 

Feldspar, the most abundant mineral in the Earth’s crust, is the name given to a group of minerals distinguished by the presence of alumina and silica (SiO2) in their chemistry.  This group includes aluminium silicates of soda, potassium, or lime. It is the single most abundant mineral group on Earth.  They account for an estimated 60% of exposed rocks, as well as soils, clays, and other unconsolidated sediments, and are principal components in rock classification schemes. The minerals included in this group are the orthoclase, microcline and plagioclase feldspars.  If you are searching for Feldspar at this location you will find it to be predominantly an ochre colour, looking like a dirty pale brown, though it can be other colours.

 

Olivine is another one of the most common minerals in the earth, and is a major rock forming mineral. Despite this, good specimens and large crystals are uncommon and sought after. Only few localities yield large examples of this mineral, although small and microscopic grains are found worldwide. Olivine is also found in meteorites, and large grains have been reported in many of them.  Olivine is not scientifically classified by the as an individual mineral type, but is rather recognized as a mineral group with the Forsterite and Fayalite members. Fayalite and Forsterite create a solid solution series, and most specimens identified as Olivine fall somewhere in between this series, almost always leaning more towards Forsterite with a greater content of magnesium. Olivine is name after its predominant colour of green, it tends to be quite clear and if you found olivine at this location you would have no doubt what it was.

So if you have been paying attention and read the information above you should be able to answer these questions.

  1. Please describe the rock face which is on the other side of the path to the wall. Please concentrate on the vein(s) of mineral which flow almost vertically through the rock, including the colour and thickness of the deposit.
  2. Please tell me if the line of mineral deposit is Feldspar, Olivine or Quartz and give an explanation for your answer.
  3. Please tell me the approximate height of the rock boulders in which the mineral vein is running through

If you feel willing and able, you are welcome to add a photo of your visit, but this is not obligatory and please make sure that your photos do not give away any answers.

 

Thank you so much for walking up to attempt this EarthCache, it is a significant undertaking and there are not many other caches around to make the trip worth-while.

I can recommend the caches on top of Craig-y-Garn, a steep climb which will reward you with magnificent views.

Happy Caching

terboR

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