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| Keywords: The Quarterly journal of the Geological Society of London (13937127022).jpg NODULAR FELSTONES OE THE LLEYN <br> 263 <br> Near the south-east corner of the Pen-y-chain promontory agate- <br> nodules occur in beds which are much contorted and are appa- <br> rently slaggy lava-flows Some of the nodules are large while <br> others more crowded together vary only from about inch to \ inch <br> across Close by a rock-mass occurs thickly set with small almond- <br> shaped white quartz-nodules usually \ inch or smaller sometimes <br> a hollow shell lined with pyramidal quartz ” white or clear golden <br> These nodules appear under the microscope sharply limited fig 8 <br> Pig 8 ” Diagram of Amygdaloids from old lava-flow at south-east <br> of Pen-y-Chain Enlarged 16 diameters <br> – if V- 'fe 1 <br> T i ' \t' i' -i'- i- y <br> V <br> a <br> W <br> V <br> The amygdaloids are filled mainly with crystalline quartz The outer grains <br> are small ; those of the interior are larger and clearer In one example <br> the cavity is partially empty a The devitrified ground-mass contains <br> remains of porphyritic felspars b <br> although some of the quartz-grains transgress the boundary <br> Radial strise of small enclosures may occur towards the exterior and <br> one example has minute microliths ranged approximately along <br> straight lines in two directions which cross at a high angle The <br> opinion might perhaps be advanced that the rounded nodules are a <br> variety of pseud-amygdals since adjacent structures have a radialized 36940056 113696 51125 Page 261 Text 45 http //www biodiversitylibrary org/page/36940056 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 36940056 dc identifier http //biodiversitylibrary org/page/36940056 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 N02/13937127022 2015-08-26 05 55 36 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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