The Farquhar Memorial EarthCache
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Memorial was commissioned by the Farquhar family of Hallgreeen Castle and is dedicated to the seafaring men of Gourdon. Erected by James Farquhar in 1871. Memorial includes Admiral Fitzroy’s Prize Medal Barometer, inscription on the plaque underneath it reads, “In memory of William Farquhar Lieut R.N. lost in the wreck of H.M. ship Racehorse off the coast of Shantung Gulf of Pechili China on the 4th Nov 1864 in his 24th year"
The memorial is of Persley Granite and the plaque is marble.
Rocks are divided into three main groups, sedimentary, Igneous and metamorphic. Two of which are found here, igneous and metamorphic.
Granite is a common intrusive plutonic igneous rock. Intrusive means that it has moved into other rocks by force coming up from the mantle. Plutonic means that it is magma that does not reach the surface of the earth and so cools very slowly underground. Igneous, derived from the Latin word ignis meaning fire, Igneous rock is formed through the cooling and solidification of magma or lava. Because it cools slowly crystals have time to form. Its name comes from the Latin word granum which means “a grain” for the coarse grain crystalline structure of the rock. Individual mineral grains are visible to the naked eye in all types of granite. It is made up of quartz, mica, and feldspar. It comes in a wide variety of colours including reds, browns, and many shades of grey from almost black to nearly all white.
There are different types of granite. The type of granite a particular specimen is, depends upon the percentages of minerals that make up the rock, especially quartz (Greyish colour), K-feldspar (Redish colour), Na-feldspar (White) and Biotite (Black). Granite must contain at least 20% quartz within a rock to make it granite. Quartz is one of the last minerals to form in granite; it acts as a bond between other minerals. Although quartz is colourless, it often appears grey because it reflects the colours of dark and light minerals around it.
There are some dark marks on the rear (facing the sea) side of the memorial, these are bits of other rocks which did not melt when they fell into the magma as it pushed its way up through the rocks. When the magma cooled these dark patches were all that was left of these rocks and are called xenoliths.
Metamorphic rocks are sedimentary or igneous rocks that have been altered by changes in temperature and/or pressure and / or chemical processes, usually while buried deep below the Earth’s surface. Exposure to these extreme conditions has altered the mineralogy, texture, and chemical composition of the rocks. New minerals grow in response to these changes and their composition depends on the composition of the original rock, and the temperatures and pressures that affect it. Marble is a metamorphic rock and when marble is formed with very few impurities it is white in colour. There are many different types of marble, based on the location and colour of the stone, It is usually a light colour, marble that contains impurities such as clay minerals, iron oxides or bituminous material can be bluish, grey, pink, yellow or black in colour. The veins and swirls present in many marble pieces occur when various mineral impurities mix with the original rock, natural marble will show its impurities through these long sinewy streaks.
To claim this earthcache, please send the answers to the questions below to us by email / message centre - do not post in your online log. Your log may be deleted if this criteria is not met. Educational guidelines for Earthcaches are set by Geocaching.com and GeoSociety.org (Earthcache) and have to be adhered to. It is helpful if you send your answers at the same as you log your find. While not compulsory it is always good to see photos of your visit.
1) Stand back a bit and look at the memorial, what would you say is the main colour of the memorial?
2) Now get up close and look at the base, what is the colour of the largest crystals you see and approximately how large are they?
3) How does the colour of the base differ to that of the column?
4) How many and what size are the xenoliths as described in the above text? (Found on the sea facing side)
5) Now have a look at the marble plaque, what is the main colour and what has caused this colour?
6) How would you describe the pattern on the marble, is it swirls, streaks, veins, cloudy or a mix of several.
Additional Hints
(Decrypt)
Hfr gur frngf gb fvg naq unir n tbbq ybbx !