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| Keywords: The Quarterly journal of the Geological Society of London (14095887953).jpg REV E HILL ON THE ROCKS OP GUERNSEY 413 <br> the only place known to me where it is worked For building-pur- <br> poses granite is actually imported from Jersey This Cobo rock is <br> however very handsome and if sound would make a very fine mate- <br> rial for the architect It is pink coarsely crystalline with felspar <br> crystals ranging from ¢ to '4 inch long and consists of flesh-coloured <br> felspar with much granular quartz and a sprinkling of black mica <br> Proof that this is truly igneous might seem needless yet it has <br> been described Cambr Phil Soc Proc vol iii p 78 as only an <br> altered state of the red gneiss so evidence must be given A bank- <br> cutting on the Cobo Road some quarter of a mile from the coast <br> shows grey gneiss and granite in almost immediate contact ; and <br> in the latter a caught-up fragment of the former The granite is <br> however greatly decomposed and so split in places by platy jointing <br> that it much resembles gneiss ; only colour and composition marked <br> the fragment If then this evidence be unconvincing let the doubter <br> Fig 2 ” Gneiss caught wp in Cobo Granite Shore south of Hommet <br> Barracks <br> Granite <br> ls » – – <br> I YAsa <br> examine the shore south of Hommet barracks fig 2 Here among the <br> rocks bared by a falling tide the granite may be seen in actual con- <br> tact with the gneiss that occupies the rest of Yazon Bay The two <br> is perfectly different ; there is no difficulty in distinguishing them <br> The pink forms insulated masses in the grey runs irregularly into <br> it flows round and includes portions of it and presents all the <br> regular appearances of igneous intrusion <br> The relation of the Cobo granite to the rocks on its east and north <br> is less easy to settle In a quarry at the west end of Les Genats <br> Eoad there appears to be a contact between the blue dioritic rock <br> which is quarried and granite If so the granite should be the <br> later as it seems to show a considerable alteration in character along <br> the contact while the blue rock remains un changed At the northern <br> limit in Portinfer Bay it is intersected by a couple of bands of a <br> dioritic rock different from the common blue variety but I see no <br> evidence to show which is the later In a quarry east of Yale church <br> is a dyke of pink granite that resembles the Cobo rock On the <br> whole I have little doubt that the Cobo granite is later than the <br> diorites <br> aJ S No 159 2e <br> h 36941232 113697 51125 Page 413 Text 40 http //www biodiversitylibrary org/page/36941232 1884 Geological Society of London Biodiversity Heritage Library The Quarterly journal of the Geological Society of London v 40 1884 Geology Periodicals Smithsonian Libraries bhl page 36941232 dc identifier http //biodiversitylibrary org/page/36941232 smithsonian libraries Information field Flickr posted date ISOdate 2014-04-30 Check categories 2015 August 26 CC-BY-2 0 BioDivLibrary https //flickr com/photos/61021753 N02/14095887953 2015-08-26 05 51 19 cc-by-2 0 PD-old-70-1923 The Quarterly journal of the Geological Society of London 1884 Photos uploaded from Flickr by Fæ using a script | ||||
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