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| Keywords: The Quarterly journal of the Geological Society of London (13889137599).jpg 16 PROF T G BOXNET ON THE GEOLOGY <br> alDundaiit a laminated yellowish green mineral occurring in isolated <br> folia in grains exhibiting a marked scaly cleavage and in felted <br> aggregates Yiewed with the polarizer alone it is seen to be mode- <br> rately dichroic a dull green when the lines formed by the cleavage- <br> planes are parallel with the vibration-plane of the transmitted beam <br> and yellow-green when they are perpendicular to it We may <br> safely regard this mineral as a species of the chlorite group 2 A <br> granular mineral often dusty-looking giving when clear fairly <br> bright tints with the two nicols This I have no doubt is epidote <br> 3 Quartz in rather irregular granules frequently containing micro- <br> liths of a pale green mineral ; some of these I have little doubt are <br> flakes of a chlorite but others appear to be belonites minute elongated <br> prisms The comparative thickness of the including quartz grains <br> renders it most difficult to examine their optical characters ; but I <br> think that the greatest extinction is when the belonite forms a small <br> angle with the vibration-plane of one of the crossed nicols so that <br> they are probably hornblende The quartz also contains numerous <br> extremely minute cavities ; these generally seem to be empty but <br> in a very few I have detected little moving bubbles 4 A mineral <br> in grains of moderate size present but in variable amount in most <br> of the slides It has one well-marked cleavage and another making <br> with it an angle not far from 90° It may be orthoclase but I <br> should have expected this under the circumstances to show more <br> indication of decomposition and I should consider that a few earthy- <br> looking grains occasionally present are more likely to represent a <br> felspathic constituent The present mineral has considerable resem- <br> blance to my specimens of kyanite which would be a mineral very <br> likely to occur in a rock of this nature Calcite grains of iron <br> Pig 8 ” Section of Chloritic Schist from the west side of Prawle <br> Point X 50 <br> peroxide and ferrite stains are occasionally and variably present <br> The quartz granules often have a very clastic aspect but as they <br> contain frequent microliths of the green constituent I consider this <br> illusory the result of subsequent pressure It will be remembered 36940735 113697 51125 Page 16 Text 40 http //www biodiversitylibrary org/page/36940735 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 36940735 dc identifier http //biodiversitylibrary org/page/36940735 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 N02/13889137599 2015-08-26 05 51 40 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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