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II.―On some specimens of Gabbro from the Pennine Alps

Published online by Cambridge University Press:  14 March 2018

T. G. Bonney*
Affiliation:
St. John's College, Cambridge

Extract

Some time since Capt. Marshall Hall called our attention to Arolla, in the Pennine Alps, as a locality interesting to mineralogists. I venture, then, to offer you a brief note on one-of its rocks, collected during a visit in the summer of 1875.

At the head of the Combe d' Arolla rises the grand mass of the Mount Colon, a truncate cone of precipitous rock, dominating the glaciers of Vuibez and Arolla, which, after sweeping down from the watershed of the Pennine chain, unite into one stream at its base. The highest point of its snowy cap is 12,264 feet above the sea. In the Swiss geological map the greater part of the mountain is coloured as gabbro, and the same rock forms a small peak near the head of the Otemma glacier on the S.W., and the S.W. flank of the Dents de Bertol to the N.E.

Type
Research Article
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1878

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References

page 5 note * Min. Mag., vol. 1., p. 61, Feb., 1877.

page 6 note * See my paper, Quart. Journ. Geol. Soc., xxxiii, p. 895.

page 6 note † Ibid., p. 889.

page 6 note ‡ The boundary between it and the diallage being sharply defined, or its being enclosed by grains of olivine or felspar.

page 6 note ‖ Analysed by Mr. Hudleston :–

Some of this magnesia may be due to minute fibrous hornblende which is probably present, but, as Mr. Hudleston observes, the result looks as if the original mineral had been anorthite.

page 7 note * Quart. Journ. Geol. Soc., xxxiii, p. 895.

page 7 note † Bulletino del Club Alpino Italiano 1868, p. 299.

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