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IV.—Woodwardian Museum Notes: on some Anglesey Dykes. II.

Published online by Cambridge University Press:  01 May 2009

Alfred Harker
Alfred Harker
Affiliation:
Fellow of St. John's College.
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Extract

In the northern half of Anglesey occur several intrusions of dark hornblendic rocks, some specimens of which were placed by Henslow in the collection made by him for the Woodwardian Museum. These rocks present a type unusual in Britain, and show some peculiarities which are of considerable interest.

A few years ago Professor Bonney found on the south-west coast of the island some boulders of a rock which he described under the name of Hornblende-picrite. It was subsequently pointed out by Professor Hughes that the probable source of these rocks was to be found in certain intrusive masses near Llanerchymedd, and indeed such boulders are scattered about rather abundantly in that neighbourhood and to the south-west. The rock in question seems, however, to be the common type of the larger eruptive masses in the north of Anglesey, and brief notes on slides cut from selected specimens taken in place may be found not unprofitable. The rocks were noticed and megascopically described in Henslow's Memoir.

Type
Original Articles
Information
Geological Magazine , Volume 4 , Issue 12 , December 1887 , pp. 546 - 552
Copyright
Copyright © Cambridge University Press 1887

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References

page 546 note 3 Q. J. G. S. vol. xxxvii. p. 137, 1881: vol. xxxix. p. 254, 1883: vol. xli. p. 515, 1885.Google Scholar See also Teall, , “British Petrography,” pp. 81, 82; plates iv. and vi. 1886.Google Scholar

page 547 note 1 Trans. Phil. Soc. Camb. vol. i. 1822.Google Scholar

page 547 note 2 Q. J. G. S. vol. xxxviii. p. 26, 1882.Google Scholar

page 550 note 1 Amer. Journ. Sci. 05, 1887, 3rd ser. vol. xxxiii. p. 385.Google Scholar

page 550 note 2 Tscherm. Min. II. Petr. Mitth. vol. v. part ii. 1883.Google Scholar

page 550 note 3 Q. G. G. S. vol. xli. plate xvi. fig. 2, 1885.Google Scholar

page 552 note 1 The resemblance even extends to the ‘solution-planes’ in the brown hornblende, parallel to the clinopinacoid (010). The slides from Pen-y-rhiwiau, however, contain an abundance of pale grass-green actinolite in blades and fan-shaped bundles.