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| Keywords: The Quarterly journal of the Geological Society of London (14073282461).jpg ASSOCIATED KOCKS OF THE BREIDDEN HILLS <br> 541 <br> Fig 3 ” Fehpar-cnistal in andesite at N end of Moel-y-Golfa <br> 00 ft from summit showing fractarea of crystal a and inclitsion <br> of serjpentine b <br> Fig 4 ” -Edge of felspar crystal showing inclusions of base <br> v\ <br> «v AA <br> 2 Pyroxene There are two forms of this mineral present <br> a Rhombic pyroxene in octagonal or elongated sections indicating <br> a good development of pinacoidal faces truncated by those of the <br> prism There is a good cleavage parallel to the best-developed <br> pinacoid but no trace of any other cleavage The crystals are ter- <br> minated by oblique faces probably domes which are generally only <br> developed at one end of the crystal The structure is slightly <br> fibrous and there are curious lamellae of darker green mineral gene- <br> rally parallel to the principal pinacoid It is slightly dichroic <br> passing from greenish yellow when the cleavage is parallel to the <br> short axis of the nicol to light straw-yellow when placed at right <br> angles The maximum extinction takes place when the cleavage is <br> parallel to one of the vibration -planes of the crossed nicols and the <br> polarization colours are not of a very high order It occurs in <br> crystals of all sizes retaining its shape do'w n to the smallest prisms It <br> is best observed in its unaltered state in the great crags running round <br> the E and S E side of the hill at a vertical distance of from 300 to <br> 400 feet from the summit but in an altered state it occurs in almost <br> all the lavas being replaced by a green or brown serpentinous <br> pseudomorph in the manner so admirably figured by Mr W Cross <br> The serpentine needles frequently have a radial arrangement and <br> there is more alteration in the large than in the smaller crystals <br> Bulletin United States Geol Suit I 1885 pi ii fig 8 37047421 114009 51125 Page 541 Text 41 http //www biodiversitylibrary org/page/37047421 1885 Geological Society of London Biodiversity Heritage Library The Quarterly journal of the Geological Society of London v 41 1885 Geology Periodicals Smithsonian Libraries bhl page 37047421 dc identifier http //biodiversitylibrary org/page/37047421 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 N02/14073282461 2015-08-26 04 55 18 cc-by-2 0 PD-old-70-1923 The Quarterly journal of the Geological Society of London 1885 Photos uploaded from Flickr by Fæ using a script | ||||
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