Geocache Description:
The coastal path here cuts across a beach, from Trinity Beach, which gives the name to the area. On this granite outcrop there is a frequently visited overlook with a bench. To the left towards the beach you will find the earthcache.
Granite is an igneous rock with grains large enough to be visible with the unaided eye. It forms from the slow crystallization of magma below Earth's surface. Granite is composed mainly of quartz and feldspar with minor amounts of mica, amphiboles, and other minerals.
QUARTZ
Quartz is the second most abundant mineral in the Earth's continental crust, after feldspar. It is made up of a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO2.
There are many different varieties of quartz, some of which are semi-precious gemstones. Particularly in Europe and the Middle East, varieties of quartz have been the most commonly used minerals in the making of jewelry since antiquity.
QUARTZ VEINS
Quartz is often found in veins that cut through rocks. Although the term "vein" suggests this, the veins of quartz and other minerals are usually not thin tubes, but rather thin sheets.
The veins can form under various conditions, and depending on these conditions, may or may not bear quartz crystals in them.
Even though certain types of quartz veins never bear any quartz crystals, it sometimes makes sense to follow large quartz veins to look for crystal-bearing fissures: Should a rock that contains old large quartz veins have been folded later due to tectonic forces, the quartz veins represented a disturbance (a discontinuity in the otherwise homogeneous mechanical properties), and alpine-type fissures are likely to open up between the quartz and the host rock.
The simplest type of a quartz vein is the filling of an already present crack in rocks. The crack might form during folding of the rock in mountain-building processes, by shattering during tectonic events, by a decrease in pressure during the uplift of a rock, or because a rock cools down and shrinks. Hot brines that percolate the rocks and originate at greater depths with higher temperatures will precipitate the minerals they carry with them in cracks at lower temperatures and pressures.
This process may continue until the crack is completely filled or may stop before, leaving "pockets" in the vein that are sometimes outlined by crystals. Hot brines that enter a crack in the rock from some distant hot source like a granite pluton first cool and precipitate most of their load rather quickly.
The result is milky quartz, either massive or made of interlocked milky quartz crystals. Later, when the crystal growth slows down, the crystals may get less milky or even clear. In the majority quartz veins, most of the quartz is precipitated as massive, milky quartz, and some crystals, if found at all, are only a small portion of the vein filling.
THE EARTHCACHE
This earthcache takes you to a granite outcrop, where you can observe several big quartz veins.
In order to log this Earthcache as a find you have to search nearby on the granite outcrop and send a e- mail or message via our profile with a respose to the following
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ON SITE, ESTIMATE the thickness of the quartz veins here? What colours are in the quartz.
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Do most of the largest of these veins form in cracks OR at random places in the magma flow?
A PHOTO looking out to sea, within the log is required but please do not post photos that show the answers of the Earthcache! Thank you.
After sending the answers by e-mail or message centre you can log the Earthcache. You will be contacted to cornfirm or clarify your answers ASAP.
~IF YOU DO NOT COMPLETE THE LOGGING TASK YOU LOG WILL BE DELETED WITHOUT NOTICE
WELL DONE to "___MandyLou25___" on 'FTF' !!!
