Plumtree War Memorial

Plumtree's War Memorial stands near the west gate of St Mary's churchyard. 

It commemorates the men from Plumtree, Normanton-on-the-Wolds and 

Clipston-on-the-Wolds who died in the two World Wars.

The west face of the plinth is inscribed with the names of the eighteen 

casualties of the First World War. The south face of plinth has the names 

of the four casualties of the Second World War and one further casualty 

of the First World War.

Compulsory tasks 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.

You won't need a magnifying glass or anything like that to complete the earthcache but if you have one, or ideally a hand lens or even a magnifying app on your smartphone, you'll be able to see the makeup of the rock in much greater detail.

1) Look at the granite memorial, here you can see phenocrysts. Please describe their size, shape, and colour.

2) Which mineral gives the phenocrysts their colour.

3) Using the information below, please tell me whether you think this rock cooled quickly or slowly, give your reasoning for your answer?

4) Are the phenocrysts anhedral or euhedral - please explain why you think this?

5) Also: 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

Granite is a common type of igneous rock. Igneous rock  is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rock is formed through the cooling and solidification of magma or lava. Igneous rock may form with or without crystallisation either below the surface as intrusive (plutonic) rocks or on the surface as  extrusive (volcanic) rocks. 

It is composed mainly of three minerals: quartz, feldspar, and mica. 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

These crystals form when magma, rich in dissolved minerals, cools slowly underground. As the magma cools, the minerals within it start to crystallise. However when the cooling process is gradual, the crystals have time to grow larger than the surrounding minerals creating phenocrysts, they contrast sharply in size with the enclosing groundmass; this implies a size ratio of at least about 5:1.

Phenocrysts provide valuable information about the conditions under which the rock formed and the history of volcanic activity in the area. Euhedral phenocrysts are characterised by well-defined crystal faces and sharp edges, indicating that they had enough space to grow freely within the magma before it solidified. On the other hand, anhedral phenocrysts lack distinct crystal faces and appear irregular in shape, suggesting that they formed in a confined space or in a rapidly cooling environment where crystal growth was hindered.

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