Quartz stone circle on the Isle of Man
This Earthcache is about Quartz.
Quartz is the second most abundant mineral in Earth's crust, after feldspar. Its crystal structure is a continuous framework of silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra.
There are many different varieties of quartz, several of which are semi-precious gemstones. Since antiquity, varieties of quartz have been the most commonly used minerals in the making of jewelry and hardstone carving, especially in Europe and the Middle East.
Crystal habit and structure
Quartz belongs to the trigonal crystal system. The ideal crystal shape is a six-sided prism terminating with six-sided pyramids at each end. In nature quartz crystals are often twinned, distorted, or so intergrown with adjacent crystals of quartz or other minerals as to only show part of this shape, or to lack obvious crystal faces altogether and appear massive. Well-formed crystals typically form in a 'bed' that has unconstrained growth into a void; usually the crystals are attached at the other end to a matrix and only one termination pyramid is present. However, doubly terminated crystals do occur where they develop freely without attachment, for instance within gypsum. A quartz geode is such a situation where the void is approximately spherical in shape, lined with a bed of crystals pointing inward.
α-quartz crystallizes in the trigonal crystal system. β-quartz belongs to the hexagonal system, space group. These space groups are truly chiral (they each belong to the 11 enantiomorphous pairs). Both α-quartz and β-quartz are examples of chiral crystal structures composed of achiral building blocks. The transformation between α- and β-quartz only involves a comparatively minor rotation of the tetrahedra with respect to one another, without change in the way they are linked.
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Crystal structure of α-quartz (red balls are oxygen, grey are silicon)
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Quartz is a mineral found in Igneous rock (like currants in a fruit cake). All of the silica and oxygen that make quartz came originally from the insides of stars, and it shot out of the stars when the stars exploded as supernovas. Then the silica formed part of a nebula, a dust cloud floating in space. Nobody knows exactly how the silica got to Earth from the nebula, but once it did, it sank down under the lighter elements of Earth (oxygen and hydrogen, and carbon) but stayed above the heavier elements such as Iron. So silicon got stuck in the middle - not in the core, but not on the surface either. In this middle zone, it was hot enough to melt rock. Most of the silica on Earth is still in this melted state. Only a little of it has gotten close enough to the surface to cool down and become solid crystals like quartz in granite.
There are many different kinds of quartz, depending on exactly how it cooled down. Some kinds have large crystals, and some have very small crystals. Small amounts of other materials that get into the stone can give it colors - quartz with a little iron in it is a pink color or a purple color called amethyst. Some kinds of quartz are nearly transparent (you can see through them).
When people want quartz today to make things out of, they often make it themselves in hot furnaces, rather than digging it out of the ground. By controlling the process, people can make perfectly even quartz with no irregularities. People use perfect quartz to make digital watches and computer microprocessors. Most glass is made by melting sand made of tiny bits of quartz.
Quartz also found in other kinds of rocks. Some igneous rocks, like granite, have quartz in them. Some sedimentary rocks, like sandstone and limestone, also contain quartz. And some metamorphic rocks, like marble, have quartz in them too.
To claim this Earthcache:
Please answer the following questions and email me or message me your answers. You can claim the cache straight away as per Earthcache guidelines. However if your answers are poor or if it is clear you haven't been to GZ your log may be deleted.
1. Describe the white rocks at GZ. In terms of number, colour, size, texture and composition. Do you see any layers in the rock?
2. What percentage of the rock to you think is quartz? What other mineral/ minerals do you think may be present?
3. What is the chemical formula of quartz?
4. Explain how you think Igneous Rocks are formed.
5. Assuming these large pieces of quartz were originally inside large pieces of granite- how do you think that they have come to be free from their Granite host? .
6. The Isle of man is often referred to as a lump of slate in the middle of the sea. With that in mind do you think these rocks were formed on the island? These rocks are Erratics so this will help you with your answer. If you do not think they are local where do you think they are from?
7. Take an elevation reading at GZ
Optional but desirable:
8. Take a photo of yourself by one of the stones. Please do not give any answers away with your photo.
Thanks for visiting and I hope you enjoyed the view.