This is an EarthCache, NO box exists, NO log to sign but to claim it as a find you MUST answer some questions and email us the answers, if you do not follow these instructions WE WILL DELETE YOUR LOG!
Granite
Granite is an intrusive igneous rock with large crystals (minerals) easily seen by the naked eye. Granite colors are most commonly pink, white, variations of grey and black.
Intrusive rock means that molten rock cooled within the crust and was never expelled as molten rock. The gradual cooling of molten rock is imperative to create the large crystals of a singular mineral that we see in granite. With time, there is differential lithification or solidifying of molten rock dependent on chemical makeup, this allows for different types of minerals to form at different periods of time and alter the final resulting granite. Therefore, the size of individual grains is proportional to how slowly the molten rock was cooled.
Igneous rock is formed through the cooling and solidification of magma or lava.
Granite is a conglomerate of minerals and rocks, primarily quartz, potassium feldspar, mica, amphiboles, and trace other minerals. Granite typically contains 20-60% quartz, 10-65% feldspar, and 5-15% micas (biotite or muscovite). The minerals that make up granite give it the unique colours we see in different types of granite.
Cornish Granite
The Cornubian batholith is a large mass of granite rock, formed about 280 million years ago, which lies beneath much of the south-western peninsula of Great Britain. The main exposed masses of granite are seen at Dartmoor, Bodmin Moor, St Austell, Carnmenellis, Land's End and the Isles of Scilly. The intrusion is associated with significant quantities of minerals particularly cassiterite, an ore of tin which has been mined since about 2000 BC. St Ives is at the eastern end of the exposed mass at lands end.
The intrusion of this granite into the surrounding sedimentary rocks is associated with significant mineralization, particularly tin, for which the area has been famous since about 2000 BC. and which led to Cornwall being one of the most important mining areas in Europe until the early 20th century.
Pedn Olva Hotel
The steps lead down to Pedn Olva ('lookout headland') hotel was built on the site of the engine house from a copper mine (Wheal Providence). The remains of a granite wall to protect the mid-19th century mine adit from the sea are still visible from Porthminster Beach.
In Order to claim this find we require you to answer a few simple questions. Please send your answers to our email address via our profile or through the message centre on geocaching.com. :
The above co-ordinates take you a set of granite steps. One third of the way up (9 steps) on the left-hand wall there is a large granite block about 63 cm by 43 cm.
1) Describe this block
2) Measure the crystals, giving the rough size of largest crystals on this block
Below left of this block is a larger granite block about 91 cm by 43 cm
3) Describe the differences between the two blocks
4) Measure the crystals, giving the rough size of largest crystals on this block
5) Give reasons why the two blocks are different.
Go down the steps and look along the wall below the steps you will see some discoloration on the granite
6) Describe the White areas and what are they are
Walk along the road away from St Ives centre you come to a platform looking down over Porthminster Beach, enjoy the views
7) Whilst it is NOT necessary to upload a photograph of your visit in order to log this Earthcache, we would love to see photos of you, or your GPS looking down at the beach.