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| Keywords: The Quarterly journal of the Geological Society of London (12893460475).jpg Yol 53 GRANITE FROM THE MIDDLE CHALK OF BETCHWORTH 217 <br> felspar are more or less cracked and recemented ; there are some <br> strain-shadows in the former and I am disposed to attribute a <br> cross-hatched structure which occurs ' sporadically ' in the latter <br> to the same cause The rock in short is gneissoid from pressure <br> and resembles those which are rather common in the same regions <br> as the last-named <br> ' I have compared these slices with one from the original Purley <br> boulder given to me by Prof Judd In this the felspar is more <br> distinctly idiomorphic the quartz has slightly larger cavities there <br> is hardly any mica biotite and one small grain I think of horn- <br> blende One or two zircons occur and also a few very small <br> Fig 2 ” Microscopic section of Boulder B <br> X30 <br> The dark grains are garnets containing much opacite The clear grains are <br> quartz The white mica can be recognized by its cleavage-lines The <br> rest of the slide is felspar The rather wavy dusty lines are cracks stained <br> or bordered with decomposition-products <br> minerals probably of secondary origin together with one slightly <br> larger which is oblong in form ; these I cannot identify with <br> certainty and need not discuss on the present occasion This rock <br> though less affected by pressure might have come from the same <br> region as the others I have also compared Mr Stebbing's <br> specimens with a slice from a boulder obtained by Mr Starkie <br> Gardner from the Kentish Gault which is almost wholly composed <br> of quartz and felspar and is much pressure-modified ' <br> Q J G S No 210 q 36028994 111130 51125 Page 217 Text 53 http //www biodiversitylibrary org/page/36028994 1897 Geological Society of London Biodiversity Heritage Library The Quarterly journal of the Geological Society of London v 53 1897 Geology Periodicals Smithsonian Libraries bhl page 36028994 dc identifier http //biodiversitylibrary org/page/36028994 smithsonian libraries Information field Flickr posted date ISOdate 2014-03-03 Check categories 2015 August 26 CC-BY-2 0 BioDivLibrary https //flickr com/photos/61021753 N02/12893460475 2015-08-26 17 53 47 cc-by-2 0 PD-old-70-1923 The Quarterly journal of the Geological Society of London 1897 Photos uploaded from Flickr by Fæ using a script | ||||
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