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| Keywords: The Quarterly journal of the Geological Society of London (13937138052).jpg NODULAR FELSTONES OF THE LLEYN <br> 265 <br> gested those which have been denned by spheroidal cracks forming <br> around gas-vesicles as explained by Professor Bonoey in felsites of <br> North Wales I have from near Pwllheli one beach-specimen <br> apparently formed by a similar process It is a devitrified rhyolite <br> with fluidal structure somewhat chalcedonized and has patches of <br> perlitic formations with viridite deposit The nodules in this specimen <br> are half aD inch or smaller oval in shape and contain quartz-filled <br> vesicles fig 10 The quartz is traversed by lines of enclosures <br> Pig 10 ” Nodules not spherulitic in a ground-mass which shows at <br> places Perlitic Cracks with Viridite deposit From the beach <br> towards Pen-y-Chain Enlarged 3 diameters <br> The crust of the nodule has a fluidal structure and is more opaque along an <br> exterior zone The interior is filled up with granular chalcedony ; but in <br> one example the nodule encloses porphyritic felspars <br> with moving bubbles and the lines pass from grain to grain as in <br> the example figured by Mr Cole f The lines are parallel to the <br> longer diameter of the nodules as would result if the enclosures <br> had originated from the action of pressure in the way described by <br> Prof Judd The edge of the nodule for a little way inwards is <br> more opaque but otherwise the crust is similar to the surrounding <br> mass and exhibits a fluidal lamination like that described by Prof <br> Bonney in nodules from near Conway § One of the spheroidal <br> cracks seems to have formed partially around a group of broken <br> porphyritic felspar something like the crack around olivine described <br> by Mr Rutley A somewhat different explanation for these <br> nodules was suggested to me as a possibility by Prof Bonney ” that <br> fragments of the lava crust enclosing vesicles might have been <br> Quart Journ Geol Soc 1882 vol xxxviii p 295 <br> t Ibid 1886 vol xlii p 188 <br> X Ibid 1885 vol xli p 376 <br> § Ibid 1882 vol xxxviii p 294 <br> Proc Roy Soc 1886 p 437 36940058 113696 51125 Page 263 Text 45 http //www biodiversitylibrary org/page/36940058 1889 Geological Society of London Biodiversity Heritage Library The Quarterly journal of the Geological Society of London v 45 1889 Geology Periodicals Smithsonian Libraries bhl page 36940058 dc identifier http //biodiversitylibrary org/page/36940058 smithsonian libraries Information field Flickr posted date ISOdate 2014-04-21 Check categories 2015 August 26 CC-BY-2 0 BioDivLibrary https //flickr com/photos/61021753 N02/13937138052 2015-08-26 05 55 03 cc-by-2 0 PD-old-70-1923 The Quarterly journal of the Geological Society of London 1889 Photos uploaded from Flickr by Fæ using a script | ||||
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