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Mineralogy at Dolgoch Falls EarthCache

Hidden : 05/08/2019
2 out of 5
1.5 out of 5

Size: Size:   other (other)

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Geocache Description:

This EarthCache is located at the beautiful Dolgoch Falls, for the purposes of this EarthCache you do not need to dwell on the waterfall too much, though it is still nice to look at. 

We are here to take a look at the minerals in the rock near the falls.

Stone which contains certain minerals will display the colour associated with that mineral.

Here are some minerals and the colour they would display in the stone that houses them.

The rock here at the falls is slate.


Though we expect iron to be a metal colour, greyish, when it is found in its natural state it will be a rust colour.  This is because as soon as the iron (Fe) is exposed to air it oxidises, and become Fe2O3 which is iron oxide, or rust.  Consequently when you find iron deposits at surface level, it will be brown. This oxidisation is very fast and can happen as quickly as 24hours. If iron is here you will see some of the faces of the split stone to be rust coloured in large sheets.


Copper is a lovely red colour when it is smelted and made into jewels or pots.  We’re used to seeing it this way but this is not what it looks like when it is dug out of the ground.  Copper ore tends to be quite green in colour and this is because the pure copper (Cu) oxidises when it comes into contact with Oxygen to produce Cu2O (there are other derivatives of Copper oxides but they are rare).  The process of copper oxidisation is quite slow and from the ore being exposed to air it can take several years to show a clear blue green colour.  If there is copper here you will see clear green stripes in the rock strata and chunks of rock which are blue green, even chunks which look like molten bits of metal.


Aluminium ore is called Bauxite and Aluminium (Al) is the most abundant metal on Earth. Despite this, it is expensive, largely because of the amount of electricity used up in the extraction process. Aluminium ore is called bauxite. The bauxite is purified to yield a white powder, aluminium oxide, from which aluminium can be extracted.  I would advise that you search for images of Bauxite ore to see if it matches the rock formation you can see before you, however, a quick description is a lumpy rock with what look like marbles embedded in it, there marbles will be pale yellow or white in colour depending how long they have been exposed.

In order to log a find against this EarthCache you will need to make some observations and send your answers to me through my Geocaching profile or through the Messenger facility.

1) You need to make your way to the viewing platform for the Lower Dolgoch Falls. The area has been greatly affected by slate mining throughout the centuries. To the left of the falls you will see a large hole, inside this hole is the rock you need to take a look at. What colour is this rock overall? 

2) Does this rock show any discoloration ?

3)What kind of mineral do you believe this rock is rich in? How would you describe it?

Additional Hints (No hints available.)