ABERDEEN ~ The Granite City #1 Lang Stane EarthCache
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This granite menhir type standing stone is set into an alcove at the SE corner of Langstane Place and Dee Street the stone was probably part of a stone circle, the conclusion taken as the base has been carved into a keel shape- common of recumbent stone circles found in Aberdeenshire, which usually date to approximately 3000BC. On Paterson's Map of the Burgh of Aberdeen printed in 1746 prior to the construction of Langstane Place, the stone can be seen in approximately its current location,though it does not appear as part of a stone circle.
There are more than 30 Aberdeens scattered across the world, but there’s only one Granite City. The North East of Scotland’s geological base is granite and Aberdeen IS the Granite City. Granite buildings are everywhere, ranging from the grandest of monuments to the humblest of tenements. The city of Aberdeen, not only known as 'the granite city' but also the Grey City and the Silver City with the Golden Sands is built extensively of silver-grey granite,( which can sparkle like silver because of its high mica content) from quarries within and around the city.
The most famous city quarry is Rubislaw which produced a fine grey muscovite-biotite granite. More than 50 per cent of Aberdeen’s buildings are estimated to have come from the Rubislaw Quarry alone, and at the industry’s peak there was so much rock produced that other British cities benefitted from it as well, including Portsmouth and Southampton, whose docks are partially made of granite, and London, where granite contributed to the construction of Waterloo Bridge and part of the Houses of Parliament. Granite from Rubislaw ( which closed in 1971) was sent to aid construction for major developments in Swindon and Leeds too.
So what exactly is granite and why is it used for building ?
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) 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. 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).
Unlike sedimentary rocks, igneous rocks do not contain any fossils. This is because any fossils in the original rock will have melted when the magma formed.
One property that affects the durability of stone is how absorbent it is. Absorbed water that freezes can have a major negative effect on stone. An analysis of granite shows that a 2-inch cube that weighs 345.5 grams will weigh 345.55 grams after a week of immersion in water. Because of this remarkably low absorption, the stone is virtually unaffected by repeated freezing and thawing. Additionally, the stone is extremely hard, with a crush strength of about 21,100 pounds per square inch. That far exceeds even high strength concrete and therefor makes an excellent building material.
To claim this earthcache, please send the answers to the questions below to us by email - 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.
1 What colour is the granite of the Langstane and what mineral do you think makes up the highest percentage in the granite?
2 What colour is the granite of the alcove ? Do you think it came from the same quarry as the Langstane ? Give reasons.
3 Look closely at the Langstane, how many different types of grain crystal do you see?
Find the largest single crystal you can, measure (or estimate) how long you think it is.
4 Rub your hand over the granite facing. Describe the texture how it feels. Is it rough, rough, smooth, or polished, does it leave any residue ?
5 Can you name any uses other then for building which granite is used for ?
And lastly while not compulsary, it is always nice to see photos of your visit
Hope you enjoyed your visit to the Langstane
(No hints available.)