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Optically uniaxial Augite from Mull

Published online by Cambridge University Press:  14 March 2018

A. F. Hallimond
A. F. Hallimond*
Affiliation:
Museum of Practical Geology, London
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Extract

The mineral hero described was recently collected by the officers of the Geological Survey during their work for the six-inch map of the Island of Mull. It is present as minute phenocrysts in a dark, glassy, magnetite-bearing rock/which is intruded as sheets in the Tertiary lavas nearly one mile south-south-west of Pennygael.

The small rounded crystals of augite are seldom more than ½ mm. in diameter and are traversed by irregular cracks. They contain a few negative crystals, and are occasionally darkened, probably with included magnetite. They appear to have been reabsorbed to some extent by the matrix.

Type
Research Article
Information
Mineralogical magazine and journal of the Mineralogical Society , Volume 17 , Issue 79 , July 1914 , pp. 97 - 99
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1914

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References

page 97 note 1 An analysis of the rock has been given in the Summary of Progress of the Geological Survey of Great Britain for 1912, 1913, p. 69 (Slice No. 15990).

page 99 note 1 Sum of molecular ratio of bases, neglecting (Al, Fe)2O3, 0.85730.

page 99 note 1 Wahl, W., Min. Pert. Mitt., 1907, vol. xxvi, pp. 1–181 Google Scholar. A somewhat similar mineral was described by Winchell, A. N., Amer. Geol., 1900, vol. xxvi, p. 199 Google Scholar, under the name of pigeonite. Cf. Lacroix, Min. de la France, 1910, vol. iv, p. 767.