This is an EarthCache which requires you to visit the location given (on the beach), gather some information by looking up at the cliff face and message/email the answers to me. You are invited to log your find at the same time as sending your answers. I will reply usually within a few days.
PLEASE BE AWARE THAT YOU CAN NOT DO THIS CACHE FROM THE GRASSED CLIFF TOP AND THERE ARE NO ACCESS POINTS DOWN TO THE BEACH CLOSE TO THE CACHE.
DO NOT ATTEMPT TO SCALE OR DECEND THE CLIFF FACE CLOSE TO THE CACHE.
So to the EarthCache lesson.
This cache is all about the minerals in the rock face and a darker line in the rock face.
From the beach location please look up at the steep rock face, look for a dark band running horizontally across the rock-face about ¼ from the top of the cliff.
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Please describe the general colour of the rock face.
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Please tell me how the band about ¼ from the top differs from the surrounding stone.
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Please tell me the mineral in rock-face and give a reason for you answer
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Please tell me why the band described above differs from the surrounding rock
Not a logging requirement but I'd like you to include a photo of yourself or GPS showing you on the beach, just to show you were there. NO SPOILERS
If you require some help deciding what you're looking at please read below.
Iron
Iron is a metallic element in the periodic table with the symbol Fe. It is the 4th most widely distributed element on the earth’s crust but is found as iron ore rather than as a useable metal. Iron ore comes in a variety of forms and looks like rock. It is a mixture of iron, oxygen and other elements, mixed in with sands and clays. When exposed to air and water iron particles in the iron ore oxidises to form FeO2 which is called, not surprisingly, iron oxide. We know this by the common term rust. If you are looking at iron oxide in the exposed rock face it will be orange in colour and the deeper the hue of orange the more iron amd therefore iron oxide is in the rock.
Lead
Lead is another metallic element in the periodic table with the symbol Pb, its ore is most commonly found as lead sulphide PbS, called galena, a heavy, shiny grey metallic ore with a obvious cubic cleavage Lead ore can also contain small amounts of silver. Lead ore occurs in two types of deposits, usually as a primary lead ore in thin veins which are called rakes, or a secondary deposit formed by weathering of the primary lead veins where the lead is washed away by water action and forms as a sediment in other rock strata. These secondary mineral deposits are often associated with ‘Neptunian dykes’, fissures in the Carboniferous Limestone in-filled with younger Triassic or Jurassic sediment. If you were to to see lead deposits in this rock face you most likely will be looking at a limestone rock with thin lead ore bands. Lead can oxidise in several forms but the most likely if PbO which is grey to dark brown and would be very easy to spot in a light coloured limestone rock. Other oxides of lead need heat.
Copper
Finally copper is yet another metallic element in the periodic table, this time with the symbol Cu. Porphyry copper deposits are copper ore rock bodies that are formed from hydrothermal fluids that originate from a large magma chamber several kilometres below the deposit itself. The fluids which carry the ore will travel up volcanic dykes or tunnels and be deposited in rock structures as they cool. As with lead, copper tends to be found in veins of a host rock which can be any sedimentary type. Copper does not react with water, but it does slowly react with atmospheric oxygen to form a layer of brown-black copper oxide which, unlike the rust that forms on iron in moist air, protects the underlying metal from further corrosion. The most common copper oxide is CuO, however there are others with more oxygen like Cu2O and Cu2O3. If you are looking at copper deposits here in the rock face however you won't find black deposits, you will in fact find bright blue/green streaks in the rock because of the gradual oxidisation process. For copper to turn from orange in its pure stage to the green/blue you would see in rock deposits takes a minimum of 20 years and can take much longer depending on the exposure to oxygen in the atmosphere.
Thanks for looking at this cache.
PLEASE TAKE CARE ACCESSING THIS CACHE FROM THE CAR PARKS ON THE CLIFF TOP, ONLY USE FOOTPATHS.
DO NOT ATTEMPT TO SCALE OR DECEND THE CLIFF FACE, IT IS VERY STEEP AND UNSTABLE.
treboR