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IV.—The So-called Serpentines of the Lleyn

Published online by Cambridge University Press:  01 May 2009

Catherine A. Raisin
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Extract

In the south-west of the Lleyn peninsula, the country inland is generally covered by drift, but the Survey map marks some isolated patches of rock as “Serpentine.” When I first visited the district, with the kind encouragement of Professor Bonney, under whom I was continuing my work at University College, I made a collection of these so-called “Serpentines” from ten different localities. The one at Porth din lleyn had been shown by Professor Bonney to be mainly diabase, and others of the examples have been since described in a previous number of this Magazine and elsewhere, but we have yet no complete account. I have, therefore, attempted to give a short summary, as preliminary to some discussion of the district.

Type
Original Articles
Information
Geological Magazine , Volume 9 , Issue 9 , September 1892 , pp. 408 - 413
Copyright
Copyright © Cambridge University Press 1892

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References

page 408 Note 1 On the Serpentine and associated Rocks of Anglesey; with a Note on the so-called Serpentine of Porth din lleyn. By Prof. Bonney, T. G., Q.J.G.S., 1881, vol. xxxvii. p. 48.Google Scholar

page 409 Note 1 Notes on the Igneous Rocks of Lleyn. By Elsden, J. V., 1888, GTEOI. MAG. Decade III. Vol. V. p. 303.Google Scholar The Bala Volcanic Series of Carnarvonshire and Associated Rocks. By Harker, A., 1889, Cambridge, pp. 83, 86–88, etc.Google Scholar

page 409 Note 2 The Monian system of Rocks. Blake, Rev. J. F., Q.J.G.S., 1888, vol. xliv. p. 531.Google Scholar The Bala Volcanic Series. Harker, A., pp. 83, 87.Google Scholar

page 409 Note 3 The Bala Volcanic Series of Carnarvonshire. Harker, A., p. 26. See also Q.J.G.S., 1889, vol. xlv. p. 253, fig. 4.Google Scholar

page 409 Note 4 Mr. Elsden, J. V., loc. cit. p. 304.Google Scholar Mr. Harker, A., loc. cit. p. 87.Google Scholar

page 410 Note 1 Mr. Elsden, J. V., loc. cit. p. 304.Google ScholarBlake, Rev. J. F., loc. cit. p. 531.Google Scholar Mr. Harker, A., loc. cit. p. 87.Google Scholar

page 410 Note 2 Mr. Elsden, J. V., loc. cit. p. 304.Google ScholarMr. Harker, A., loc. cit. p. 87.Google Scholar

page 410 Note 3 Mr. Harker, A., loc. cit. pp. 87, 88.Google Scholar

page 410 Note 4 Q.J.G.S., 1881, vol. xxxvii. pp. 48–50. Prof. Bonney, T. G..Google Scholar

page 410 Note 5 Q.J.G.S., 1881, vol. xxxvii. p. 50. Prof. Bonney, T. G..Google Scholar Compare also Q.J.G.S. 1888, vol xliv. p. 461.Google Scholar Mr. Harker, A.. The Bala Volcanic Series of Carnarvonshire. Mr. Harker, A., p. 111Google Scholar; GEOL. MAG. 1880, Vol. VII. p. 457. Mr. Reid, A. S..Google Scholar

page 410 Note 6 One of the rocks was ohtained from a boss on the grassy slope and has a bright green polished surface with streaks coloured by red halmatite. Sheep are continually rubbing themselves against the projecting stone, and the polishing is evidently due to their action.

page 410 Note 7 Mr. Elsden, J. V., loc. cit. p. 308.Google Scholar

page 411 Note 1 am much indebted to Mr. Thos. Davies, F.G.S., for kindly allowing me to see slides of the Lambay porphyry, and other Irish specimens, in the collection of the Mineralogical Department at the British Museum of Natural History.

page 411 Note 2 Mr. Harker, A., loc. cit. pp. 87, 88.Google Scholar

page 411 Note 3 The Geology of North Wales. Mem. of Geol. Survey, p. 230 (2nd ed.)

page 412 Note 1 See figures in Brit. Petrog. Teall, J. J. H., p. 14 (after Zirkel)Google Scholar; U. S. Explorations of 40th parallel. Microo. Petrog. F. Zirkel, pl. i. fig. 20; Typical Forms of Crystallites. Eutley, F.. Min. Mag. Dec. 1891, p. 268, fig. 17. Crenulites.Google Scholar