At the posted coordinates your find some granite benches surrounding the flag pole, a great place to take a pew and enjoy the view.
Logging Requirements (Questions to Answer)
In order to log a find against this EarthCache, you will need to visit GZ and make some observations and then answer some questions and send answers to me via my Geocaching profile or through the Messenger Centre.
1) Using the images below, please identify the granite that the bench seat tops are made of - pay attention to the colours, what it feels like to touch and the size of the crystals that make up the granite.
2) Using the images below, please identify the granite that the legs are made of - pay attention to the colours, what it feels like to touch and the size of the crystals that make up the granite.
3) Identity which granite has cooled the slowest, give reasons for your answer.
4) Compulsory task: Include in your log a photograph of you, your GPS or another identifiable item near GZ, taking care not to include anything in the photo that may give away your answers.
Granite.
Igneous and sedimentary rocks differ significantly in their formation processes and hardness. Igneous rocks originate from the cooling and solidification of molten magma or lava. This process, either deep within the Earth's crust (intrusive) or on its surface (extrusive), results in the formation of crystals, giving igneous rocks a generally hard and crystalline structure. On the other hand, sedimentary rocks are formed through the accumulation and cementation of sediments, such as mineral and organic particles, over time. These sediments are often derived from the weathering and erosion of pre-existing rocks. Due to their formation from loosely compacted materials, sedimentary rocks are typically softer compared to igneous rocks. The contrasting processes of solidification from molten material versus sediment compaction contribute to the distinct textures and hardness levels observed in these two major rock types.
Granite's unique composition makes it ideal for memorials, it is a very robust stone that will last for hundreds of years to come. It has the ability to withstand extreme temperatures as well as general weathering over time.
What is Granite?
Granite is a Crystalline (Contains crystals) igneous rock which is made mainly of Quartz, feldspar, mica and a small trace of other minerals. Granite has to be at least 20% quartz to be called Granite. Granite is typically: 20-60% quartz, 10-65% feldspar, and 5-15% micas. The presence of orthoclase or plagioclase in granite depends on the specific geological conditions during its formation. Orthoclase feldspar is more commonly found in granites that solidify at higher temperatures in the Earth's crust. On the other hand, plagioclase feldspar is prevalent in granites that form at lower temperatures. These feldspar minerals contribute to the overall composition and appearance of granite, with orthoclase imparting a pinkish hue and plagioclase ranging from white to grey.
Granite is an Igneous Rock... What is an Igneous Rock?
An Igneous rock is formed by the cooling of Molten rock. Igneous rock comes in two categories: 1. Intrusive and 2. Extrusive.
1. Intrusive Igneous rock occurs when the cooling of molten rock occurs under the Earth's surface. As it cools under the Earth's surface it cools slowly which enables large crystals to form. The slower the cooling the larger the crystals form.
2. Extrusive Igneous rock occurs when the molten rock cools on top of the Earth's surface. As the rock is exposed to the Earth's elements such as rain etc the rock cools quickly and if crystals form they are usually quite small. Often not visible to the naked eye.
Why are granite rocks different colours?
The relative ratio of different colored minerals in a granite is largely due to the original source of molten rock that cooled to form the granite. If the molten rock was abundant in potassium feldspar, the granite is more likely to take on a salmon pink colour. On the other hand, if the molten rock is abundant in quartz and some other minerals one may get a black and white speckled granite.
Below are some components of Granite and their colours:
- Quartz - typically milky white colour
- Feldspar - typically off-white colour
- Potassium Feldspar - typically salmon pink colour
- Biotite - typically black or dark brown colour
- Muscovite - typically metallic gold or yellow colour
- Amphibole - typically black or dark green colour
A. White Granite is composed primarily of Quartz and Feldspar. The small black specks in the granite above are likely small amphibole crystals.
B. Pink coloured granite is a result of an abundance of potassium feldspar within the granite. One can see small specs of milky semi-transparent quartz, dark brown/black amphibole, and opaque white feldspar.
C. White and black Granite often has granite appears to have equal parts quartz, feldspar, and amphibole, making a speckled white and black granite.
D. Red granite is a variation of pink potassium feldspar granite. In this instance the k-feldspar takes on a redder than pinker colour due to the colouration of the feldpsar crystals by the redder-coloured iron oxide mineral called 'heamatite' within them.
