Zetel loves Sutherland EarthCache
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A commemorative Stone on A9 northbound near the Dornoch Firth Bridge, with a long layby for parking. There is a plaque on the boulder in German, the inscription reads "Möge diese Brücke für alle Zeiten ein Symbol inniger Freundschaft des Distriktes Sutherland und der Gemeinde Zetel sein." Zetel, den 27. 08. 1991. Verein der Freunde Sutherlands e.V. Wilhelm Herrenberg (1. Vorsitzender) Translated ~ "May this bridge forever be a symbol of heartfelt friendship between the county of Sutherland and the community of Zetel." Zetel, 27. 08. 1991. The Friends of Sutherland. Wilhelm Herrenberg (chairman).
This year, 2017, also marks the 5th anniversary of the Haggis Highway, so it is good to see a cache back here at this boulder where one of the original Haggis caches was placed at the start in 2012.
A glacial erratic is a piece of rock that differs from the size and type of rock native to the area in which it rests. "Erratics" take their name from the Latin word errare (to wander), and are carried by glacial ice, often over distances of hundreds of kilometres to a different area and is left behind when the ice melts. . During their journey, erratics become worn, rounded and smooth by the ice, other rocks and stones that they rub against as they tumble along.
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) and sometimes black amphibole hornblende.
Biotite is a sub group of the mica group.Biotite is a name used for a large group of black mica minerals that are commonly found in igneous and metamorphic rocks. These include annite, phlogopite, siderophyllite, fluorophlogopite, fluorannite, eastonite, and many others. These micas vary in chemical composition but are all sheet silicate minerals with very similar physical properties. Like most of the mica group, biotite has a very organized "basal cleavage" structure, meaning that it has a tendency to split along planar lines or surfaces, forming sheets, or “lamallea “ A generalised composition for the biotite group is: K(Mg,Fe)3AlSi3O10(OH)2.
Biotite is easily identified, as it is black mica with perfect cleavage and a vitreous lustre on the cleavage faces. When held up to the light, the sheets of biotite are transparent to translucent with a brown, grey, or greenish colour.
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To claim this earthcache, please send the answers to the questions below to us by email or messenger- do not post in your online log.Your log may be deleted if these criteria are not met. Educational guidelines for Earthcaches are set by Geocaching.com and GeoSociety.org (Earthcache) and have to be adhered to.
1 a) Estimate the height and circumference of the boulder.
b) Do you think this was a glacial erratic or a boulder taken from a granite quarry? Give reasons for your answer
2 a) Examine a 15cm square area of the boulder, looking closely at the crystals, what is the average size of the quartz and the feldspar crystals?
b) What colours are the quartz and feldspar?
c) What percentage of the 15cm area is biotite?
d) Are you sure? ~ rub your fingers over the black specs; does some of it come away because it is just dirt / soot?
3 While not compulsory it is always good to see a photo from your visit
With thanks to SNH for allowing this earthcache
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